refactor(review): address PR #185 review (lease leak, tests, changelog, jsonb seam)

8-point multi-aspect review of the batch PR; security/regressions were clean.

1. Lease leak: the #180 reorder moved `toolsFor` (which leases external MCP
   clients, refCount+1) ahead of buildSystemPrompt + forUser, but the only
   release (closeExternalClients) was bound to the streamText callbacks. A throw
   in between leaked the lease (refCount stuck, undici sockets held until
   restart). Define closeExternalClients right after the lease and wrap
   buildSystemPrompt+forUser in try/catch that closes-then-rethrows.
2. Cover the patch_node/delete_node dup-id refusal (#159 #6): extract the guard
   into a pure `assertUnambiguousMatch` (node-ops) and unit-test 0/1/>1.
3. Regress the body-before-title order (#159 #10): mock-HTTP test (collab fails
   fast against a server with no WS upgrade) asserts /pages/update (title) is
   NEVER posted when the body write fails — for updatePage AND updatePageJson.
4. CHANGELOG [Unreleased]: #180, #168 (Added); #163 (Fixed).
5. Add the missing en-US i18n keys (Back to references / {{label}}).
6. Drop the duplicate content/empty/blank cases in ai-chat.prompt.spec.ts (they
   repeat the buildMcpToolingBlock unit tests); keep only sandwich placement +
   both-safety-copies.
7. CI Postgres pg16 -> pg18 (match docker-compose).
8. jsonb decode seam: shared `parseJsonbValue(value, guard)` in database/utils.ts
   holds the legacy double-encoding self-heal in one place; parseToolAllowlist /
   parseModelConfig keep only a type-guard.

Verified: server build + 124 unit + 15 integration; mcp 311; prettier clean.

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

apps/server/src/database/utils.ts

@@ -64,3 +64,29 @@ export function jsonbBind<T>(
   }
   return sql<T>`${JSON.stringify(value)}::text::jsonb`;
 }
+
+/**
+ * READ-side counterpart to {@link jsonbBind}: tolerantly decode a jsonb value
+ * read back from the DB and validate its shape with `guard`. THE single place
+ * the legacy double-encoding self-heal lives, so repos keep only a type-guard.
+ *
+ * A row written by the old `::jsonb` bind round-trips as a JSON STRING (see the
+ * quirk in jsonbBind), so the driver hands back e.g. `'["a"]'` / `'{"k":1}'`
+ * rather than the structure. This parses such a string once, then applies the
+ * caller's `guard`. Returns `null` for null / an unparseable string / a value
+ * the guard rejects (so a corrupt or wrong-shaped value degrades to "unset").
+ */
+export function parseJsonbValue<T>(
+  value: unknown,
+  guard: (v: unknown) => v is T,
+): T | null {
+  let v: unknown = value;
+  if (typeof v === 'string') {
+    try {
+      v = JSON.parse(v); // legacy double-encoded read
+    } catch {
+      return null;
+    }
+  }
+  return guard(v) ? v : null;
+}