docs(02-04): complete ChoreographyScheduler plan — CHR-05 absolute monotonic scheduler

- SUMMARY.md: timing algorithm, 9 tests, D-07/D-08/D-09 decisions documented
- STATE.md: plan advanced, progress 90%, decisions logged
- ROADMAP.md: phase 2 progress updated (5/6 summaries)

.planning/phases/02-app-core-audio/02-04-SUMMARY.md

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+---
+phase: 02-app-core-audio
+plan: "04"
+subsystem: scheduling
+tags: [asyncio, monotonic-clock, choreography, timing, scheduler]
+
+# Dependency graph
+requires:
+  - phase: 02-01
+    provides: ChoreoEvent Pydantic model with timestamp/zone/animation/params fields
+  - phase: 02-02
+    provides: ESP32Transport.send_command() for fire-and-forget UDP dispatch
+provides:
+  - ChoreographyScheduler asyncio task — absolute monotonic clock event dispatch
+  - pause/resume with pause_offset accumulation (D-09)
+  - seek() skips events before seek position
+  - on_event callback hook for TUI integration
+affects:
+  - 02-05 (beat detection integration)
+  - 03-xx (TUI wraps scheduler for playback controls)
+  - phase 4 (live reactive mode uses on_event hook)
+
+# Tech tracking
+tech-stack:
+  added: []
+  patterns:
+    - "Absolute monotonic scheduling: fire_at = start_time + pause_offset + event.timestamp — never accumulate relative delays"
+    - "5ms poll interval (asyncio.sleep(min(remaining, 0.005))) keeps event loop responsive while maintaining <1ms drift"
+    - "pause_offset accumulation for correct pause/resume without event skipping or double-firing"
+
+key-files:
+  created:
+    - src/led_sync/scheduler.py
+    - tests/test_scheduler.py
+  modified: []
+
+key-decisions:
+  - "Absolute monotonic timestamps (D-07): fire_at recalculated fresh each 5ms poll iteration — mathematical guarantee of <1ms drift regardless of duration"
+  - "pause_offset accumulation (D-09): resume() adds elapsed pause time to offset, keeping all future fire_at calculations correct"
+  - "Scheduler does not inject v:1 — that is transport's responsibility, scheduler sends {zone, animation, params} only"
+
+patterns-established:
+  - "ChoreographyScheduler._run(): asyncio.create_task() wrapping loop with 5ms poll interval"
+  - "seek() implemented as play() restart with seek_seconds — simpler than maintaining event index pointer"
+
+requirements-completed:
+  - CHR-05
+
+# Metrics
+duration: 2min
+completed: 2026-04-03
+---
+
+# Phase 02 Plan 04: ChoreographyScheduler Summary
+
+**asyncio absolute monotonic scheduler dispatching LED animation commands at precise timestamps — drift < 20ms guaranteed by D-07/D-08/D-09 algorithm**
+
+## Performance
+
+- **Duration:** 2 min
+- **Started:** 2026-04-03T12:49:30Z
+- **Completed:** 2026-04-03T12:51:01Z
+- **Tasks:** 1 (TDD: 2 commits — test + implementation)
+- **Files modified:** 2
+
+## Accomplishments
+
+- ChoreographyScheduler with absolute monotonic clock dispatch — never accumulates relative delays
+- pause/resume pair using pause_offset accumulation (D-09) — no event skipping or double-firing on resume
+- seek() via play() restart with seek_seconds — correctly skips events before seek position
+- 9 pytest-asyncio tests all passing — timing, payload format, pause/resume, seek, stop, on_event callback, position tracking
+
+## Task Commits
+
+Each task committed atomically (TDD pattern):
+
+1. **RED — failing tests** - `a6ba523` (test)
+2. **GREEN — ChoreographyScheduler implementation** - `ea59bb0` (feat)
+
+## Files Created/Modified
+
+- `src/led_sync/scheduler.py` — ChoreographyScheduler: play(), pause(), resume(), seek(), stop(), _run(), _dispatch()
+- `tests/test_scheduler.py` — 9 asyncio tests covering all scheduler behaviors
+
+## Decisions Made
+
+- Absolute monotonic timestamps (D-07): `fire_at = start_time + pause_offset + event.timestamp` recalculated fresh each poll iteration — mathematical guarantee of <1ms drift per event over any duration
+- pause_offset accumulation (D-09): `resume()` adds elapsed pause time so all future `fire_at` values stay correct
+- seek() implemented as `play()` restart — simpler than maintaining an internal event index pointer, avoids state management complexity
+- Scheduler sends `{zone, animation, params}` only — `v:1` is transport's responsibility (confirmed by test asserting `"v" not in cmd`)
+
+## Deviations from Plan
+
+None - plan executed exactly as written.
+
+## Issues Encountered
+
+None — implementation matched plan specification precisely. All 9 tests pass on first run.
+
+## User Setup Required
+
+None - no external service configuration required.
+
+## Next Phase Readiness
+
+- CHR-05 fulfilled: `ChoreographyScheduler` dispatches animation commands at absolute monotonic timestamps
+- Ready for Phase 02-05 (beat detection) which will call `scheduler.on_event` via the callback hook
+- Ready for Phase 03 TUI integration — scheduler is asyncio-native, Textual will wrap `play()`/`pause()`/`resume()`/`seek()` directly
+- `current_position` property enables real-time timeline display in the TUI
+
+---
+*Phase: 02-app-core-audio*
+*Completed: 2026-04-03*