#47 (SLICE-2, review): per-block document proposals + word-precise accept

Document-edit flow SLICE-2 (specs/coauthoring-document-edit-flow.md §7.2,
INV-39/40/41 — P1 "too much to review"). A whole-document rewrite now proposes
ONE F4 proposal per CHANGED BLOCK (the unit a human reviews), but accepting a
block reconciles attribution at WORD granularity (the unit F3 records). Block =
decision unit; word = attribution unit. Supersedes INV-37's per-word cut for
document edits; selection edits unchanged.

- trackChangesModel.ts: new pure diffToBlockHunks(current, rewritten) — block-key
  alignment (reusing diffArrays/diffBlocks keying): an isolated changed block →
  one block-aligned hunk → the rewritten block raw (a code/mermaid fence is one
  atomic whole-fence hunk, INV-23); insert/delete runs → one gap-span hunk over
  the inter-anchor region (separators included) so reconstruction stays exact; a
  zero-width gap-span is anchored (INV-41). Also split diffToHunks into the raw,
  un-anchored wordEditHunks + the anchoring wrapper (the anchoring could grow an
  insertion to overlap an adjacent hunk, corrupting a batch apply — a latent bug
  that only surfaced once hunks are applied as a batch).
- trackChangesPreview.ts: runEditAndPropose document branch uses diffToBlockHunks
  and tags each proposal granularity:"block".
- model.ts / proposalModel.ts: additive optional Proposal.granularity
  ("block"|"single"; absent ⇒ single, back-compat — no migration).
- proposalController.ts: accept of a block proposal runs an intra-block word
  sub-diff (wordEditHunks, disjoint) and applies one applyAgentEdit per changed
  run, descending offset — only the words Claude changed land Claude-attributed;
  unchanged spans keep prior authorship (INV-40).
- Tests: diffToBlockHunks unit (reconstruction + fence atomic + add/remove);
  f12Review host E2E (M blocks→M proposals, unchanged→none, fence atomic, INV-40
  attribution, INV-41 insertion accept); updated the f11 document-path E2E to
  per-block (INV-39 supersedes INV-37); MANUAL-SMOKE-F12 §2.

Seam note: pendingEdits.matchEvent resolves one registration per change event, so
INV-40's per-run attribution is sequential applyAgentEdit calls (N undo steps),
not one multi-replace WorkspaceEdit — see transcript Deferred decisions.

214 unit + 69/5 host E2E green.

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

docs/MANUAL-SMOKE-F12.md

@@ -35,3 +35,35 @@ The body and tab menus show exactly one Ask-Claude edit entry, matching the live
 selection state (selection → Edit Selection; none → Edit Document); the tab
 gesture targets the clicked tab's document, not the active editor; both are absent
 on non-markdown docs; no console errors.
+
+## SLICE-2 — #47 (review): per-block proposals + word-precise attribution (INV-39/40/41)
+
+On a markdown doc with several paragraphs, **Ask Claude to Edit Document** with a
+light copy-edit instruction (e.g. "tighten the prose, fix typos").
+
+1. **One proposal per changed block (INV-39).** Claude's pass surfaces as **one
+   ✓/✗ block per changed paragraph/header/bullet**, not a flurry of word-level
+   blocks. A paragraph with several word edits is a **single** proposal; the
+   word-level `<ins>`/`<del>` still shows *inside* it. Untouched paragraphs show no
+   proposal.
+2. **Changed fence is atomic (INV-23).** If Claude edits a code/mermaid fence, it
+   is **one** whole-fence proposal.
+3. **Accept attributes only the changed words (INV-40).** Accept a block proposal,
+   then toggle the preview to **Authorship**/colors (or re-open in the on-state):
+   only the words Claude actually changed are Claude-colored; the unchanged words
+   in that block keep their prior author. The block is the decision unit; the word
+   is the attribution unit.
+4. **Inserted block accepts cleanly (INV-41).** If Claude adds a new paragraph,
+   its proposal **accepts** (it is anchored to an adjacent block, never a
+   born-orphaned/zero-width proposal).
+5. **Undo.** Accepting a block is currently **N undo steps** (one per changed run
+   inside the block) — `Ctrl+Z` repeatedly restores it. (Spec deferred note:
+   single-undo-step grouping is a possible follow-up.)
+6. **Selection edits unchanged.** Edit *Selection* still produces exactly one
+   proposal over the selection (no block fan-out).
+
+### Pass criteria
+
+A document edit yields one in-context proposal per changed block (fences atomic);
+accepting a block lands the whole block but Claude-attributes only the words it
+changed; inserted blocks accept; selection edits are unaffected; no console errors.