docs: add requirements, roadmap, and initial state

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.planning/STATE.md

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+# Project State
+
+## Project Reference
+
+See: .planning/PROJECT.md (updated 2026-04-05)
+
+**Core value:** Load a song, build a synchronized light show, play it back live — with precise control over every effect on every device.
+**Current focus:** Phase 1 — Foundation
+
+## Current Position
+
+Phase: 1 of 7 (Foundation)
+Plan: 0 of 3 in current phase
+Status: Ready to plan
+Last activity: 2026-04-05 — Roadmap and state initialized
+
+Progress: [░░░░░░░░░░] 0%
+
+## Performance Metrics
+
+**Velocity:**
+- Total plans completed: 0
+- Average duration: —
+- Total execution time: 0 hours
+
+**By Phase:**
+
+| Phase | Plans | Total | Avg/Plan |
+|-------|-------|-------|----------|
+| - | - | - | - |
+
+**Recent Trend:**
+- Last 5 plans: —
+- Trend: —
+
+*Updated after each plan completion*
+
+## Accumulated Context
+
+### Decisions
+
+Decisions are logged in PROJECT.md Key Decisions table.
+Recent decisions affecting current work:
+
+- Init: Web UI over TUI — richer DAW interactions while keeping terminal aesthetic via CSS
+- Init: python-mpv-jsonipc preferred over ctypes binding — no libmpv.dll dependency on Windows
+- Init: Firmware deferred to Phase 7 — protocol must be validated against simulator first
+- Init: undo/redo built in Phase 4 — retrofitting command pattern is expensive
+
+### Pending Todos
+
+None yet.
+
+### Blockers/Concerns
+
+- Phase 2: python-mpv-jsonipc latency on Windows 11 under load is unbenchmarked — validate with timing harness in 02-01
+- Phase 4: librosa MP3 loading path on Windows needs explicit validation (soundfile falls back to audioread which requires FFmpeg on PATH)
+- Phase 6: AI sync approach (LLM-assisted) has no reference implementation — treat as spike, not commitment
+
+## Session Continuity
+
+Last session: 2026-04-05
+Stopped at: Roadmap created, STATE.md initialized
+Resume file: None
+
+Next action: `/gsd:plan-phase 1`