Replace the 'unstract-clone' console script with a top-level 'unstract'
Click group ('unstract clone' is now the canonical invocation), promote
click/rich from the 'clone' extra into core dependencies (the extra is
removed), and document the CLI — usage, env promotion use case, main
options and exit codes — in the README.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

New 'group' phase (runs first): clones org user groups by name with
idempotent merge — a like-named target group is always reused, never
renamed or errored — and records int-pk remaps for downstream phases.
Opt-in --clone-group-members matches members to target users by email,
bulk-adds the hits and reports the misses as warnings; service accounts
(@platform.internal) never migrate.

After each shareable resource lands (adapter, connector, workflow,
pipeline, api_deployment, custom_tool), its source share state is
mirrored via POST /{resource}/{id}/share/: shared_groups through the
group remap (axis omitted with a warning when the group phase is
excluded), shared_to_org as-is, shared_users via id -> email -> target
id (missing users skipped + warned). shared_users stays stripped from
create POSTs (SERVER_MANAGED). Users/groups listings are memoised per
run; dry-run never POSTs. Reports gain a non-fatal warnings channel.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Empty Prompt Studio projects cannot be exported (backend guard), so
they have no source registry entry and no workflow references. The
phase previously republished unconditionally, turning these into
counted failures on every run. Now the source registry lookup runs
first and the export + remap are skipped when no entry exists.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

…rd None group listing

- _cached: a raced _FETCH_FAILED no longer shadows a peer's successful
  listing (would silently no-op all share replication for the run).
- list_groups: 'or {}' guard mirrors list_users so a None response can't
  raise AttributeError.
- Add regression tests for both race directions.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

UN-3479 [FEAT] CLI restructure with user-group cloning + share-state replication