chore(deps): bump tiptap to 3.32.2 and keep headings that open a list item - #9898

Summary

• Bumps every @tiptap/* package in apps/sim from 3.31.4 to 3.32.2.
• Raises the root prosemirror-transform override from 1.12.0 to 1.12.4, since @tiptap/pm 3.32 requires ^1.12.2. 1.12.1 through 1.12.4 are bug fixes only, and 1.12.4 fixes a step-deserialization bug introduced in 1.12.3. The other prosemirror overrides already satisfy 3.32.2. Transitive prosemirror-commands/-history/-dropcursor/-changeset patch bumps come in through @tiptap/pm.
• Sim fix (list-item.ts): @tiptap/extension-list 3.32 now turns a heading at the start of a list item into the item's paragraph and drops its level. With that change, opening a file containing - # Title and saving it rewrote it as - Title. CommonMark reads - # Title as a heading inside the list item, and Sim's schema already supports that: MarkdownListItem puts an empty paragraph first. The override now parses that case as blocks itself, so the output is the same as on 3.31.4.
• @tiptap/y-tiptap stays on 3.0.7 on purpose. From 3.0.8 on, a new reconcile path pairs the unanchored children by position. When one transaction merges a block into the list after it (for example, typing - above a list, or toggleBulletList joining the list below), y-tiptap deletes the list's Y.XmlElement and recreates it. Edits a peer made inside that list at the same time are lost on every client, and the clients still converge, so nothing reports an error. The same code is still in the latest release (3.3.0). It has the same root cause as the open upstream issue y-tiptap 3.2.0: lifting a list item replaces the list's Yjs element, losing or duplicating concurrent edits ueberdosis/tiptap#8735. @tiptap/extension-collaboration 3.32.2 accepts ^3.0.7.

Type of Change

• Other: dependency upgrade (plus a markdown-fidelity fix the upgrade requires)

Testing

• rich-markdown-editor/ folder in one vitest run: 716/716 pass. With y-tiptap 3.0.9, 5 tests fail (list-collaboration join and undo tests, plus 2 image-collaboration tests). Reverting the list-item.ts fix makes heading-image (- # Before ![Logo](…) after) fail again.
• lib/collab-doc/ (the converter, seed, merge, and persist tests that use tiptap): 82/82 pass.
• Ran parse and serialize on headings in list items, setext items, blockquotes, ordered items, and the 3.32 !-before-link escape. Every case gives the same output on 3.31.4 and on 3.32.2 with the fix.
• y-tiptap: a two-editor StarterKit + Collaboration repro (B types in a list item while A runs toggleBulletList on the paragraph above). On 3.0.7 both clients keep B's text. On 3.0.9 both clients converge without it.
• bun install --frozen-lockfile is clean. The lockfile only changes @tiptap/* and the prosemirror packages.

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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