docs(02-03): complete waveform display and transport UI plan — AUD-05 fulfilled

- SUMMARY.md for 02-03 (waveform extractor + transport UI)
- STATE.md: checkpoint at human-verify task 3, decisions recorded
- ROADMAP.md: phase 2 progress updated (3/3 plans)
- REQUIREMENTS.md: AUD-05 marked complete

.planning/STATE.md

@@ -2,15 +2,15 @@
 gsd_state_version: 1.0
 milestone: v1.0
 milestone_name: milestone
-status: executing
-stopped_at: Completed 02-audio-engine/02-02-PLAN.md
-last_updated: "2026-04-06T13:08:39.827Z"
+status: verifying
+stopped_at: "Checkpoint: 02-03 Task 3 human verification — awaiting user confirmation"
+last_updated: "2026-04-06T13:15:05.979Z"
 last_activity: 2026-04-06
 progress:
   total_phases: 7
-  completed_phases: 1
+  completed_phases: 2
   total_plans: 7
-  completed_plans: 6
+  completed_plans: 7
   percent: 0
 ---
 
@@ -27,7 +27,7 @@ See: .planning/PROJECT.md (updated 2026-04-05)
 
 Phase: 02 (audio-engine) — EXECUTING
 Plan: 3 of 3
-Status: Ready to execute
+Status: Phase complete — ready for verification
 Last activity: 2026-04-06
 
 Progress: [░░░░░░░░░░] 0%
@@ -57,6 +57,7 @@ Progress: [░░░░░░░░░░] 0%
 | Phase 01 P04 | 2 | 2 tasks | 3 files |
 | Phase 02-audio-engine P01 | 525603 | 2 tasks | 5 files |
 | Phase 02-audio-engine P02 | 8 | 2 tasks | 3 files |
+| Phase 02-audio-engine P03 | 8min | 2 tasks | 5 files |
 
 ## Accumulated Context
 
@@ -82,6 +83,8 @@ Recent decisions affecting current work:
 - [Phase 02-audio-engine]: broadcast_loop accepts get_engine callable instead of direct import — avoids ws.py/main.py circular import
 - [Phase 02-audio-engine]: asyncio.to_thread for engine.load in REST endpoint — python-mpv-jsonipc load is synchronous, must not block event loop
 - [Phase 02-audio-engine]: AUD-02 (YouTube URL loading) deferred to Phase 6 — noted in docstring, not implemented in audio.py
+- [Phase 02-audio-engine]: ffmpeg subprocess pipe for MP3 waveform extraction (libsndfile/soundfile does not support MP3 natively)
+- [Phase 02-audio-engine]: Transport state driven by WebSocket tick — no frontend polling
 
 ### Pending Todos
 
@@ -95,8 +98,8 @@ None yet.
 
 ## Session Continuity
 
-Last session: 2026-04-06T13:08:39.818Z
-Stopped at: Completed 02-audio-engine/02-02-PLAN.md
+Last session: 2026-04-06T13:15:05.973Z
+Stopped at: Checkpoint: 02-03 Task 3 human verification — awaiting user confirmation
 Resume file: None
 
 Next action: `/gsd:plan-phase 1`