revert(01): reopen Phase 1 — D-13 multi-EBML-concat is unplayable

REQ-video-ring-buffer flipped from [x] back to [ ]. ROADMAP.md Phase 1
row reverted from [x] Closed 2026-05-15 to [ ] reopened 2026-05-16.
STATE.md status flipped phase_complete → phase_reopened with full
historical narrative preserved.

Root cause (confirmed at byte level by gsd-debugger 2026-05-16):
D-13's concat-of-self-contained-WebM-segments architecture produces a
3-EBML-header WebM that standards-compliant Matroska parsers
(mpv, ffmpeg, Chrome HTMLMediaElement) play only as the first segment
(~9.94 s) and silently drop the remaining 2 segments. Confirmed via
operator mpv drag-drop test of BOTH the canonical 2026-05-15 closure
fixture and the 2026-05-16 UAT-produced fixture — both exhibit the
same broken playback.

The 2026-05-15 "operator-confirmed clean Chrome playback" assessment
was insufficient: it verified the file plays without freezing but did
not measure total duration. Phase 1's primary deliverable
(REQ-video-ring-buffer / SPEC §10 #7) is therefore NOT satisfied.

Fix path chosen by user: ts-ebml (parse) + webm-muxer (write) to
replace mergeVideoSegments file-concat with real single-EBML remux.
Will land as Plan 01-08 via fresh /gsd-plan-phase ceremony.

RED test landed in tests/offscreen/webm-playback.test.ts (2 new
assertions on container-format-duration + ffmpeg-full-decode-duration).
2 failures, 53 baseline tests still GREEN.

Option C port-lifecycle refactor (debug session
empty-archive-port-race, commits 674c415..f0871c0) DID land cleanly
and is retained — that fix was orthogonal and correctly resolved the
silent-empty-archive symptom that previously masked this deeper bug.

Debug session: .planning/debug/d13-multi-ebml-concat-unplayable.md

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

.planning/STATE.md

@@ -2,16 +2,16 @@
 gsd_state_version: 1.0
 milestone: v2.0.0
 milestone_name: milestone
-status: phase_complete
-stopped_at: "Phase 1 closure 2026-05-15: D-12 ffprobe gate + A3 empirical-playback gate both green against tests/fixtures/last_30sec.webm (1.6 MB VP9 1142×1038, 3-segment multi-EBML-header concat). D-13 restart-segments retired D-09..D-11 mid-phase. 30/30 vitest green incl. empirical webm-playback dry-runs; tsc clean; ffmpeg -v warning -i fixture -f null - exit 0 with zero decoder errors (only expected muxer DTS-monotonicity warnings at segment join boundaries); operator confirmed clean Chrome playback end-to-end. REQ-video-ring-buffer marked Complete. Ready to plan Phase 2 (DOM + event-capture privacy)."
-last_updated: "2026-05-15T21:42:00.000Z"
-last_activity: "2026-05-15 — Phase 1 closure: D-12 + A3 gates green; REQ-video-ring-buffer complete; ready for Phase 2"
+status: phase_reopened
+stopped_at: "Phase 1 REOPENED 2026-05-16: D-13 multi-EBML-concat architecture confirmed broken via UAT Test 3 retest + byte-level EBML probe — produced WebM plays only ~9 s instead of ~30 s in mpv AND Chrome (the 2026-05-15 closure's operator playback check was insufficient). Phase 1's primary deliverable (REQ-video-ring-buffer, SPEC §10 #7) is NOT satisfied. Plan 01-08 (WebM remux via ts-ebml + webm-muxer) will replace mergeVideoSegments file-concat with real single-EBML remux. RED test landed in tests/offscreen/webm-playback.test.ts (2 failures, 53 baseline GREEN). Option C port-lifecycle refactor (debug session empty-archive-port-race) DID land cleanly (commits 674c415..f0871c0). Phase 1 also absorbs whole-desktop + auto-start UX (Plans 01-09/01-10) per 2026-05-16 amended charter."
+last_updated: "2026-05-16T17:35:00Z"
+last_activity: "2026-05-16 — Phase 1 reopened: D-13 multi-EBML architecture confirmed broken by mpv/Chrome playback test; Plan 01-08 (ts-ebml + webm-muxer remux) pending; markers reverted"
 progress:
   total_phases: 5
-  completed_phases: 1
-  total_plans: 7
+  completed_phases: 0
+  total_plans: 10
   completed_plans: 7
-  percent: 100
+  percent: 70
 ---
 
 # Project State