test(review): add the 4 new test-coverage points from PR #185 re-review

The re-review's blocking/structural points (lease leak, dup-id guard test,
body-before-title test, CHANGELOG, pg18, shared jsonb decoder) were already
addressed in commit 24264ef; this adds the 4 genuinely-new coverage requests:

- pt 6: `scrollToReference(id, index?)` exercised against a live editor DOM —
  selects the index-th `sup[data-footnote-ref][data-id]` occurrence, falls back
  to the first for out-of-range, returns false for an empty id (scrollIntoView
  stubbed). (#168)
- pt 7: export `backlinkLabel` and pin the base-26 carry boundary
  (25->z, 26->aa, 27->ab, 51->az, 52->ba). (#168)
- pt 8: integration fail-open — a PRESENT-but-corrupt tool_allowlist (jsonb
  string scalar holding non-array JSON) reads back as null ("no restriction"),
  covering normalizeRow's degrade branch. (#159 #172/#173)
- pt 9: getFootnoteRefCount cache invalidation — adding a `[^a]` reference bumps
  the cached count 2 -> 3. (#168)

Verified: editor-ext footnote 23; client structure 7 + tsc; server int 8.

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

apps/server/test/integration/ai-mcp-server-repo.int-spec.ts

@@ -91,6 +91,25 @@ describe('AiMcpServerRepo tool_allowlist jsonb round-trip [integration]', () =>
     const healed = enabled.find((r) => r.id === id);
     expect(healed?.toolAllowlist).toEqual(['alpha', 'beta']);
   });
+
+  it('FAIL-OPEN: a present-but-corrupt tool_allowlist reads back as null (no restriction)', async () => {
+    // #185 re-review pt 8: normalizeRow's fail-open branch — the column is
+    // PRESENT but does not parse into a string[] (here a jsonb string scalar
+    // holding non-array JSON). The read must degrade to `null` ("no restriction"),
+    // not crash. (A warn is logged with the server id; not asserted here.)
+    const id = randomUUID();
+    await sql`
+      INSERT INTO ai_mcp_servers (id, workspace_id, name, transport, url, tool_allowlist)
+      VALUES (
+        ${id}, ${ws}, ${`srv-${id}`}, 'http', 'https://example.com/mcp',
+        to_jsonb(${'{"not":"an array"}'}::text)
+      )
+    `.execute(db);
+    // Sanity: the column is present (a jsonb string scalar), not SQL NULL.
+    expect(await jsonbTypeof(id)).toBe('string');
+    // ...yet the read degrades to null (fail-open).
+    expect((await repo.findById(id, ws))?.toolAllowlist).toBeNull();
+  });
 });
 
 /**