Three issues from the PR review:

1. Codex P1: buildClosedEdgeLoop only checked graph degree, so any
   closed cycle of selected edges (e.g. the perimeter of an existing
   face) passed through. Filling such a cycle stacked overlapping
   triangles on the live geometry. Added a per-edge boundary check
   (each selected edge must touch exactly one face) before the loop
   walk, refusing interior-edge cycles upfront.

2. CodeRabbit Major: HalfEdgeMesh::fillSelection's duplicate-triangle
   check was gated on n == 3, leaving n > 3 fans free to recreate
   existing tris on their first sub-triangle. Replaced the gate with a
   per-fan-triangle check: every (apex, v_i, v_{i+1}) tri is checked
   against existing faces incident to the apex. Added a regression
   test (FillSelectionRejectsLargerFanThatDuplicatesExistingTri).

3. Codex P2 / CodeRabbit Major: the F shortcut accepted the event
   whenever the selection looked fillable, even when fillSelection()
   returned 0 (e.g. interior edge loop after fix #1, or duplicate-
   triangle rejection after fix #2). Now only swallows the keypress on
   a non-zero return — so F still falls back to Frame-Selection when
   the fill is rejected.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* feat(edit): subdivide + fill (Phase 4 topology ops)

Implements the remaining Subdivide and Fill items from issue #259.

HalfEdgeMesh:
  - subdivideFaces: 1-to-4 split with shared midpoints between selected
    faces and T-junction-aware retriangulation of adjacent triangles
    (1/2/3 split-edge cases all handled).
  - fillSelection: 3-N vertex fan-triangulation for vertex fills and
    closed boundary edge loops; refuses cross-submesh, duplicate-tri,
    and orphaned-only inputs.

EditModeController:
  - subdivideSelection wires Face mode (selected tris) and Edge mode
    (incident tris of selected edges) to the HE primitive, captures
    midpoint positions to re-select after the round-trip pack, and
    pushes one EditMeshTopologyCommand for undo.
  - fillSelection wires Vertex mode (set order = fan order) and Edge
    mode (closed-loop detection via degree-2 walk).

UI:
  - Two new toolbar buttons (Subdivide ⊞, Fill ◆) with mode-aware
    enable/visibility.
  - F shortcut fills in edit mode when the selection is fillable;
    otherwise falls through to the existing Frame-Selection behavior.

Tests:
  - 15 new HalfEdgeMesh standalone tests covering both ops, including
    T-junction handling, UV interpolation, cross-submesh rejection,
    and round-trip safety.
  - 7 new controller tests guarded by tryInitOgre (skip on macOS,
    run on Linux CI).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(rtss): register only one RTShaderLib path to avoid duplicate parse

addRTSSResources() registered up to 4 candidate directories, deduplicated
only by canonical path. On macOS dev builds the bundle's interior media/
and the dev-copy at bin/media/ are distinct paths with identical contents,
so both got registered. Ogre re-parses .program scripts per resource
location, and the second pass over ShadowVolumeExtude.program raised
ItemIdentityException on the duplicate Ogre/ShadowBlendVP GpuProgram,
aborting startup.

Pick the FIRST existing RTShaderLib + sibling Main pair and stop. Both
copies hold the same files, so the order doesn't matter functionally —
this just avoids the double-registration.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* test(edit): expand subdivide/fill coverage + document Phase 4

HalfEdgeMesh tests (+8):
  - subdivide every cube face stays closed-manifold
  - subdivide preserves blended bone weights at midpoints
  - splitMask=2 path verified on the quad neighbor
  - cross-submesh subdivide leaves submesh 1 untouched
  - non-adjacent multi-face selection on a cube
  - fill caps a deleted cube face back to closed
  - fill accepts orphaned vertices (post-delete hole-cap flow)
  - fill round-trip safe through toEditableMesh/buildFromEditableMesh

Controller tests (+3):
  - subdivideSelection in edge mode promotes incident faces
  - fillSelection in vertex mode produces a new triangle
  - fillSelection pushes an undo command

Docs:
  - CLAUDE.md keyboard shortcut line notes F's dual role and X/Ctrl+X
    in Edit Mode
  - New "Edit Mode (Phase 4 topology)" section summarising the
    EditModeController + HalfEdgeMesh op set, with a targeted note on
    Subdivide and Fill

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(edit): address Codex P1/P2 + CodeRabbit Major review

Three issues from the PR review:

1. Codex P1: buildClosedEdgeLoop only checked graph degree, so any
   closed cycle of selected edges (e.g. the perimeter of an existing
   face) passed through. Filling such a cycle stacked overlapping
   triangles on the live geometry. Added a per-edge boundary check
   (each selected edge must touch exactly one face) before the loop
   walk, refusing interior-edge cycles upfront.

2. CodeRabbit Major: HalfEdgeMesh::fillSelection's duplicate-triangle
   check was gated on n == 3, leaving n > 3 fans free to recreate
   existing tris on their first sub-triangle. Replaced the gate with a
   per-fan-triangle check: every (apex, v_i, v_{i+1}) tri is checked
   against existing faces incident to the apex. Added a regression
   test (FillSelectionRejectsLargerFanThatDuplicatesExistingTri).

3. Codex P2 / CodeRabbit Major: the F shortcut accepted the event
   whenever the selection looked fillable, even when fillSelection()
   returned 0 (e.g. interior edge loop after fix #1, or duplicate-
   triangle rejection after fix #2). Now only swallows the keypress on
   a non-zero return — so F still falls back to Frame-Selection when
   the fill is rejected.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Addresses Codex P1 findings on PR #578:

## P1 #1 — diff against captured bind positions, not the live buffer

`addMorphTargetFromCurrentEdit` was diffing `EditableMesh` against
positions read from the entity's current GPU vertex buffer. But
edit-mode ops (translate / rotate / scale) call `commitToEntity`
during the gesture — both sides of the subtraction end up identical
in the common flow, so `slice.offsets` stays empty and the command
incorrectly returns no-op even after visible edits.

Fix: snapshot the bind positions once at `EditableMesh::loadFromOgreMesh`
time (`EditableSubMesh::originalPositions`). The snapshot is never
mutated by edit-mode ops, so `vertices[i].position -
originalPositions[i]` recovers the right delta regardless of how
many commits have run since enter-edit-mode.

## P1 #2 — shared-vertex submeshes

The old `readBindPositions` rejected any submesh with
`useSharedVertices=true` (vertexData null in that case). Most
Mixamo-style assets use shared vertices, so morph authoring silently
skipped them.

Fix is implicit in #1: `loadFromOgreMesh` already copies the shared
vertex pool into each affected submesh's `vertices` array; the new
`originalPositions` snapshot is built from that same source, so
shared-vertex submeshes carry their own baseline. The GPU-buffer
read path goes away entirely.

## CodeRabbit minor — null-assert SelectionSet in tests

Added `ASSERT_NE(sel, nullptr)` before `sel->append(entity)` in the
three new authoring tests, matching the slice-A1 pattern. If the
singleton ever fails to initialize, we get a clear assertion failure
instead of a null-deref crash.

## Tests

- `LoadFromEntityTriangleMesh` extended to assert (a) the snapshot
  matches `vertices[].position` after load and (b) mutating
  `vertices[].position` does NOT touch `originalPositions`. Exercises
  the shared-vertex case (the triangle fixture uses shared verts).
- New `AddMorphTargetUndoableViaUndoManager` exercises the full
  add → undo → redo loop through the shared `UndoManager`, with a
  hand-built slice that mirrors what `addMorphTargetFromCurrentEdit`
  will produce once edit-mode capture is wired up end-to-end.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

…#578)

* feat(morph): sub-slice A3 — authoring (add from edit, rename, delete)

Last remaining sub-slice of #518. Closes the morph epic's authoring loop:
users can save the current edit-mode geometry as a new morph target,
rename existing targets, and delete unwanted ones. All three operations
are undoable.

## What ships

### `commands/MorphCommands.{h,cpp}` — three QUndoCommand subclasses
- `AddMorphTargetCommand` — create N same-named Ogre::Pose entries (one
  per submesh) plus a matching VAT_POSE Animation. Slices come in as
  sparse `{submeshHandle, {vertexIndex: Vector3f}}` maps so the command
  doesn't depend on EditableMesh — anything that produces deltas can
  drive it (current edit, MCP, future "fix mirror axis" rules…).
- `DeleteMorphTargetCommand` — snapshot the same-named pose offsets at
  construction, drop the pose(s) + Animation + AnimationState on redo,
  rebuild from the snapshot on undo.
- `RenameMorphTargetCommand` — same snapshot-and-rebuild pattern, just
  with a different name on the rebuild side. Ogre 14.5 doesn't expose
  Pose::setName, so destroy-and-recreate is the only path.

### `MorphAnimationManager` — three new Q_INVOKABLE methods
- `addMorphTargetFromCurrentEdit(name)` — reads `EditModeController`'s
  live EditableMesh, diffs every submesh against the mesh's bind
  positions on the GPU buffer, builds the slice list, pushes an
  AddMorphTargetCommand. Falls back to no-op if not in edit mode, no
  vertices moved, or name collides.
- `renameMorphTarget(old, new)` — name-trim, collision check, push.
- `deleteMorphTarget(name)` — existence check, push.

All three resolve the entity from SelectionSet's first entity (same
pattern as the A1/A2 setters), push onto the shared `UndoManager`
stack so Ctrl+Z reverses, and emit `morphTargetsChanged` so the
Inspector re-fetches.

## Tests

8 new GTest cases on `MorphAnimationManager_test.cpp`:
- Add command creates + undoes pose and Animation cleanly.
- Delete command round-trips (poses restored on undo).
- Rename command round-trips (old name restored on undo).
- Rename rejects target-name collisions, no-op self-renames, blank names.
- Delete rejects unknown / empty names; succeeds on a real target.
- Add-from-edit rejects empty / whitespace names before edit-mode check.
- Add-from-edit returns false when no EditableMesh is available
  (i.e. user isn't in edit mode).
- All three methods reject when nothing is selected.

The command path is what's actually under test — the manager wrappers
are thin selection + name-validation glue. We keep direct command
tests because that's where the undo / redo contract lives and it
exercises the pose snapshot / rebuild path without needing an Inspector.

## What's deferred

- **Inspector UI** (Add / Rename / Delete buttons in the Morph Targets
  subgroup) — small but lives in QML, and the last QML change in this
  epic (A5's dope-sheet integration) deterministically crashed
  unrelated tests for reasons I never fully isolated. Doing the UI in
  a separate PR keeps blast radius contained.
- **MCP tools** `add_morph_target` / `rename_morph_target` /
  `delete_morph_target` — straightforward but adds surface; can land
  alongside the Inspector UI.
- **CLI** `qtmesh morph --rename / --delete` — needs export-after-edit
  plumbing through the FBX/glTF morph exporters from A4a/A4b.

#518 status after this slice:

| Sub-slice | Status |
|-|-|
| A1 — Importer + manager + CLI list | shipped (#569) |
| A2 — Inspector subgroup | shipped (#570) |
| A3 — Authoring | **this PR** |
| A4a — glTF export | shipped (#573) |
| A4b — FBX export | shipped (#575) |
| A5 — Controller API | shipped (#576) |
| A5b — Dope-sheet UI | follow-up |
| A6 — MCP tools | shipped (#571) |
| A3b — Inspector / MCP / CLI authoring surface | follow-up |

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(build): add MorphCommands.cpp to tests/ source list

Linker errors on the secondary test binaries (MaterialEditorQML_test,
MaterialEditorQML_qml_test, MaterialEditorQML_perf_test) because they
compile MorphAnimationManager.cpp (which now references the three
MorphCommand constructors) but didn't pick up MorphCommands.cpp.
src/CMakeLists.txt has it; tests/CMakeLists.txt was missing the line.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* review(morph): A3 — capture bind positions on EditableMesh load

Addresses Codex P1 findings on PR #578:

## P1 #1 — diff against captured bind positions, not the live buffer

`addMorphTargetFromCurrentEdit` was diffing `EditableMesh` against
positions read from the entity's current GPU vertex buffer. But
edit-mode ops (translate / rotate / scale) call `commitToEntity`
during the gesture — both sides of the subtraction end up identical
in the common flow, so `slice.offsets` stays empty and the command
incorrectly returns no-op even after visible edits.

Fix: snapshot the bind positions once at `EditableMesh::loadFromOgreMesh`
time (`EditableSubMesh::originalPositions`). The snapshot is never
mutated by edit-mode ops, so `vertices[i].position -
originalPositions[i]` recovers the right delta regardless of how
many commits have run since enter-edit-mode.

## P1 #2 — shared-vertex submeshes

The old `readBindPositions` rejected any submesh with
`useSharedVertices=true` (vertexData null in that case). Most
Mixamo-style assets use shared vertices, so morph authoring silently
skipped them.

Fix is implicit in #1: `loadFromOgreMesh` already copies the shared
vertex pool into each affected submesh's `vertices` array; the new
`originalPositions` snapshot is built from that same source, so
shared-vertex submeshes carry their own baseline. The GPU-buffer
read path goes away entirely.

## CodeRabbit minor — null-assert SelectionSet in tests

Added `ASSERT_NE(sel, nullptr)` before `sel->append(entity)` in the
three new authoring tests, matching the slice-A1 pattern. If the
singleton ever fails to initialize, we get a clear assertion failure
instead of a null-deref crash.

## Tests

- `LoadFromEntityTriangleMesh` extended to assert (a) the snapshot
  matches `vertices[].position` after load and (b) mutating
  `vertices[].position` does NOT touch `originalPositions`. Exercises
  the shared-vertex case (the triangle fixture uses shared verts).
- New `AddMorphTargetUndoableViaUndoManager` exercises the full
  add → undo → redo loop through the shared `UndoManager`, with a
  hand-built slice that mirrors what `addMorphTargetFromCurrentEdit`
  will produce once edit-mode capture is wired up end-to-end.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>