docs(01-11): close as spike-pivot — SUMMARY landed, AMENDMENT-A deleted, pivots to 01-13

Closes Plan 01-11 honestly per GSD spike-pivot pattern. Original
Approach A (Puppeteer sw.evaluate per RESEARCH §1+6) empirically
falsified across Wave 3 execution + feasibility research. Approach B
(extension-internal-page harness + offscreen synthetic stream) proven
via c647f61 prototype; full implementation moves to Plan 01-13.

What this commit does:
- ADDS 01-11-SUMMARY.md (spike-then-pivot framing per GSD artifact-
  types.md PLAN→SUMMARY lifecycle; captures retained infrastructure,
  falsified hypotheses, working prototype, bridge to 01-13)
- REVERTS frontmatter amendment block in 01-11-PLAN.md; replaces with
  closed_as/pivoted_in/closure_note pointing at SUMMARY + 01-13
- DELETES 01-11-PLAN-AMENDMENT-A.md (improvised artifact type — not
  recognized in GSD artifact-types.md; content folded into SUMMARY)

Lesson for orchestrator (captured in SUMMARY §Architectural Notes):
when a plan attempts an approach that proves infeasible, the right
move is honest SUMMARY + new plan, NOT in-place rewrite + AMENDMENT
artifact. The project's own pattern (01-08, 01-09, 01-10, 01-11
added mid-phase as new work surfaced) confirms add-new-plan-when-
scope-shifts is the established pattern.

Plan 01-09 closure via harness PASS NOT achieved by 01-11; still
requires operator UAT pending Plan 01-13 landing.

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

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

@@ -1,7 +1,8 @@
 ---
-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-amendment_summary: "Wave 1 T2 + Wave 2 T3 + Wave 3 method guidance superseded.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."
+closed_as: "spike-pivot"
+closed_at: "2026-05-18"
+pivoted_in: "01-13"
+closure_note: "Approach A (Puppeteer sw.evaluate per RESEARCH §1+6) empirically falsified; pivoted to Approach B (extension-internal-page harness, proven by c647f61 prototype) in Plan 01-13. See 01-11-SUMMARY.md for full pivot rationale + retained infrastructure."
 phase: 01-stabilize-video-pipeline
 plan: 11
 type: tdd