fix(comment): store the real anchored substring as expectedText + pin authz (#318 F1/F2)

F1 [blocking]: a suggestion whose anchor matched via normalization could never
be applied (spurious 409). The comment mark lands on the doc's ACTUAL text
(Docmost auto-converts to typographic quotes/dashes/nbsp), but the stored
selection — used as expectedText at apply — was the raw ASCII agent input
(+substring(0,250)). So replaceYjsMarkedText's strict joined!==expectedText
always failed and threw "text changed" though nobody edited. Fix: new pure
getAnchoredText(doc, selection) reconstructs the exact raw doc substring the mark
covers (slicing identical to spliceCommentMark); on the suggestion path
client.createComment stores THAT as selection, so expectedText equals the marked
text and apply returns applied:true. Live anchoring still uses the raw agent
selection (normalization still finds the anchor). Truncation raised 250->2000
(+ DTO @MaxLength(2000)) so the anchored substring is never cut below the mark
span. Ordinary comments unchanged. AI-chat shares client.createComment, so
covered. Regression tests: getAnchoredText raw-vs-ASCII; create payload selection
is the typographic substring; apply with typographic expectedText -> applied.

F2 [blocking]: added comment.controller.spec.ts pinning that validateCanEdit runs
before applySuggestion (Forbidden -> applySuggestion never called; happy path ->
called; missing comment -> 404 without authorizing).

MCP 448 pass; server comment+yjs 54 pass. MCP build/ rebuilt.

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

apps/server/src/collaboration/yjs.util.spec.ts

@@ -379,6 +379,32 @@ describe('replaceYjsMarkedText', () => {
     expect(text.toDelta()).toEqual(before);
   });
 
+  // F1 regression: the marked doc text is TYPOGRAPHIC (smart quotes / em-dash)
+  // and expectedText equals that raw typographic text — as it now does, because
+  // the MCP client stores the RAW anchored substring (getAnchoredText) rather
+  // than the agent's ASCII input. The strict `joinedText !== expectedText`
+  // compare must therefore MATCH and the suggestion apply (not a spurious 409).
+  it('typographic marked text applies when expectedText is the raw typographic text', () => {
+    const marked = '“hello”—world';
+    const { fragment, text } = buildRuns([
+      { text: 'say ' },
+      { text: marked, comment: { commentId: 'c1', resolved: false } },
+      { text: '!' },
+    ]);
+
+    const result = replaceYjsMarkedText(fragment, 'c1', marked, 'bye');
+
+    expect(result).toEqual({ applied: true, currentText: 'bye' });
+    expect(text.toDelta()).toEqual([
+      { insert: 'say ' },
+      {
+        insert: 'bye',
+        attributes: { comment: { commentId: 'c1', resolved: false } },
+      },
+      { insert: '!' },
+    ]);
+  });
+
   it('anchor deleted: no mark with that commentId → { applied: false, currentText: null }', () => {
     const { fragment, text } = buildWithComments([
       { text: 'abc', comment: { commentId: 'c1', resolved: false } },