docs(01-11): amendment A — pivot to extension-internal harness page

Architectural pivot triggered by feasibility research prototype
(commit c647f61, A6 PASS 5/5 + Bug-B regression rewind verified).

Two empirical findings invalidate original architecture:
1. MV3 service workers BLOCK dynamic import. await import('test-hooks/
   sw-hooks') in src/background/index.ts silently kills the SW —
   chunk loads, await never resolves, no listeners register. Cited
   Chromium es_modules.md + w3c/webextensions#212.
2. Puppeteer WebWorker.evaluate against MV3 SW only exposes chrome.
   {loadTimes,csi} — not the extension chrome.* API surface.

The Wave 1 (cb1a729) SW-side hooks are fundamentally broken in test
builds (production unaffected — gated by __MOKOSH_UAT__ which is
false in prod). Executor must DELETE the SW-side dynamic import +
sw-hooks.ts entirely; offscreen-side hooks stay (offscreen IS a DOM
document; dynamic import works there).

Replacement (Verdict-A architecture, proven by prototype):
- Extension-internal harness page at chrome-extension://<id>/tests/
  uat/extension-page-harness.html — privileged extension context
  with FULL chrome.* API access
- Puppeteer drives the page via page.goto + page.evaluate
- For SW state: page calls chrome.runtime.sendMessage; SW responds
  via production messaging
- For getDisplayMedia: offscreen-side installFakeDisplayMedia() patches
  navigator.mediaDevices.getDisplayMedia → Canvas captureStream
  synthetic MediaStream

A6 (Bug B regression catch) PROVEN. Industry-standard pattern (MetaMask,
eyeo, Chrome MV3 official testing docs all converge).

Effort remaining: ~7-10h subagent budget (Wave 0 + bonus debug-import
commits keep; Wave 1 hooks rewire 30min; Wave 2 scaffolding 1-2h;
Wave 3 13 more assertions 4-6h; Wave 4 closure 1h).

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

.planning/phases/01-stabilize-video-pipeline/01-11-PLAN.md

@@ -1,4 +1,7 @@
 ---
+amended_at: "2026-05-18"
+amendment: "A"
+amendment_summary: "Wave 1 T2 + Wave 2 T3 + Wave 3 method guidance superseded. MV3 SW blocks dynamic import (verified empirically); SW-side test hooks DROPPED. Replaced with extension-internal harness page architecture (proven by c647f61 prototype). See 01-11-PLAN-AMENDMENT-A.md."
 phase: 01-stabilize-video-pipeline
 plan: 11
 type: tdd