feat(01-11): wave-1 — gated test hooks for SW + offscreen, dist/ stays hook-free

Task 2 of Plan 01-11 (Puppeteer UAT harness).

Test hook surface:
- src/test-hooks/types.ts: canonical MokoshTestSurface — handlers
  (onClicked, onStartup, notificationOnClicked), notificationCount,
  lastNotificationOptions<true>, notificationIds, getCurrentStream,
  getSegmentCount. globalThis.__mokoshTest ambient declaration.
- src/test-hooks/sw-hooks.ts: SW-side hook. Monkey-patches addListener
  on chrome.action.onClicked / chrome.runtime.onStartup / chrome
  .notifications.onClicked to capture handler refs while chaining to
  the original. Wraps chrome.notifications.create across all four
  overload shapes (id+options+cb, options+cb, id+options→Promise,
  options→Promise) to increment notificationCount, save
  lastNotificationOptions, push resolved id into notificationIds.
- src/test-hooks/offscreen-hooks.ts: offscreen-side hook. Exports
  setCurrentStream + setSegmentCountGetter; the recorder calls both
  inside startRecording after the mediaStream + segments assignments.
  getCurrentStream getter closes over the cell so the harness reads
  the live MediaStream for displaySurface inspection + 'ended'
  dispatch (Bug B BLOCKER per RESEARCH §7).
- tests/uat/lib/test-hook-contract.d.ts: manual harness-side mirror of
  MokoshTestSurface (decoupled from src/ to keep tests/ import-clean
  per RESEARCH §11 resolution 5; drift risk documented inline).

Production-side wires (gated by __MOKOSH_UAT__ token):
- src/background/index.ts top-of-module: `if (__MOKOSH_UAT__) { await
  import('../test-hooks/sw-hooks'); }`. MUST run before any chrome.*
  addListener call below — top-of-module placement satisfies this.
- src/offscreen/recorder.ts top-of-module: symmetric gated dynamic
  import + module-scoped testHooks reference.
- src/offscreen/recorder.ts inside startRecording (after mediaStream
  assignment): `if (__MOKOSH_UAT__) { testHooks?.setCurrentStream(stream);
  testHooks?.setSegmentCountGetter(() => segments.length); }`
- src/offscreen/recorder.ts inside onUserStoppedSharing (after
  mediaStream = null): `if (__MOKOSH_UAT__) { testHooks?.setCurrentStream(null); }`
  — T-1-11-05 (Repudiation: stale stream ref) mitigation.

Build-time token wiring:
- vite.config.ts: declares `define: { __MOKOSH_UAT__: 'false' }` (prod
  default) + bumps `build.target: 'es2022'` so the top-level await in
  the gated dynamic imports compiles (MDN: Chrome 89 / Edge 89 /
  Firefox 89 / Safari 15 support TLA; MV3 floor Chrome 88 is
  effectively Chrome 89+ in field — comfortably inside the envelope).
- vite.test.config.ts: overrides `define: { __MOKOSH_UAT__: 'true' }`
  so the test bundle has the hooks active.
- vitest.config.ts: declares `define: { __MOKOSH_UAT__: 'false' }` for
  vitest's own source-loading runs. CRITICAL — without this, vitest
  would throw `ReferenceError: __MOKOSH_UAT__ is not defined` when
  loading src/background/index.ts; OR if we'd used `import.meta.env.MODE
  === 'test'` (RESEARCH §6's initial guidance), vitest's default
  MODE='test' would have ACTIVATED the hooks under unit tests +
  clobbered every existing vi.fn() chrome.notifications.create mock.
  The dedicated `__MOKOSH_UAT__` token sidesteps both failure modes
  cleanly — a refinement on RESEARCH §6 documented in the comment
  preambles of all three configs.
- globals.d.ts: declares `__MOKOSH_UAT__: boolean` ambient so
  `npx tsc --noEmit` passes without per-file annotations.
- tsconfig.json: include adds `globals.d.ts`.

Notification options generic refinement:
- chrome.notifications.NotificationOptions is declared with a
  `<true | false>` generic distinguishing "create" (all required —
  true) from "update" (all optional — false). Plan 01-11's production
  code always uses the create shape; types.ts + sw-hooks.ts pin to
  `NotificationOptions<true>` so the harness reads iconUrl etc. as
  definitely-present.

Verification:
- npx tsc --noEmit: exit 0
- npm run build: exit 0
- grep -rln '__mokoshTest\|simulateUserStop\|getSegmentCount\|setCurrentStream\|setSegmentCountGetter' dist/:
  ZERO matches (Tier-1 gate stays GREEN)
- npm run build:test: exit 0; dist-test/ emits separate sw-hooks-*.js
  + offscreen-hooks-*.js chunks (the gated dynamic imports survive
  tree-shaking when __MOKOSH_UAT__ === true)
- grep -rln '__mokoshTest' dist-test/: 2 matches
  (assets/sw-hooks-*.js + assets/offscreen-hooks-*.js)
- SKIP_BUILD=1 npx vitest run: 89/89 GREEN
  (83 baseline + 6 Tier-1 hook-leak surfaces)
- sw-bundle-import.test.ts: GREEN (the gated dynamic import does not
  break production module init — the `if (false)` branch is never
  reachable so the await + import are dead code in dist/)

In-flight bugs auto-fixed (Rule 1 + Rule 3):
- Rule 3: original RESEARCH §6 plan called for `import.meta.env.MODE
  === 'test'` as the gate; switched to `__MOKOSH_UAT__` define-token
  after observing vitest contamination (vitest defaults MODE='test'
  → hooks activated under unit tests → 8 existing tests broke with
  "Cannot read properties of undefined (reading 'calls')" because the
  hook wrapper replaced vi.fn() mocks). Documented in the comment
  preambles of all three configs as a refinement on RESEARCH §6.
- Rule 3: esbuild rejected TLA against the default ES2020 target;
  bumped to es2022 (Chrome 89+ supports TLA per MDN — inside MV3
  envelope). Recorded in vite.config.ts preamble.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/background/index.ts

@@ -10,6 +10,26 @@ import type {
 import { remuxSegments } from './webm-remux';
 import JSZip from 'jszip';
 
+// ─── Plan 01-11: gated test-hook dynamic import ───────────────────────
+// MUST run BEFORE any chrome.* addListener call below so the SW-side
+// test hook's addListener monkey-patches catch every handler
+// registration. The `__MOKOSH_UAT__` token is text-replaced by Vite at
+// build time — `false` in production (vite.config.ts), `true` only in
+// the test bundle (vite.test.config.ts). The `if (false)` branch is a
+// static dead branch and Rollup tree-shakes the entire `await import`
+// away (Plan 01-11 RESEARCH §6, refined: we use a dedicated token
+// rather than `import.meta.env.MODE === 'test'` because vitest also
+// runs with MODE='test' and gating on MODE would activate the hooks
+// inside unit tests + clobber their vi.fn() chrome.* mocks).
+//
+// The Tier-1 grep gate `tests/background/no-test-hooks-in-prod-bundle
+// .test.ts` enforces that `__mokoshTest` is absent from every file
+// under `dist/` post-build (T-1-11-01 — Elevation of Privilege via
+// leaked hook surface).
+if (__MOKOSH_UAT__) {
+  await import('../test-hooks/sw-hooks');
+}
+
 // Default MIME applied when a wire chunk somehow lacks a type
 // field (defense-in-depth: in normal operation the offscreen recorder
 // always populates it from chunk.data.type). Matches D-20 strict codec.