docs(02): create phase plan — 3 plans across 3 waves

.planning/ROADMAP.md

@@ -47,8 +47,12 @@ Plans:
   3. Drone layer amplitude rises and falls with traffic volume over time — sustained traffic sounds louder, quiet periods fade
   4. User can specify output path via `-o` flag; it defaults to `netsynth-<timestamp>.mp3` when omitted
   5. An empty (zero-packet) input produces a clear error message instead of a corrupt or zero-byte MP3
-**Plans**: TBD
-**UI hint**: no
+**Plans:** 3 plans
+
+Plans:
+- [ ] 02-01-PLAN.md — Environment setup (gcc, ffprobe, go-lame), synth config table, oscillator, EMA layer with tests
+- [ ] 02-02-PLAN.md — Stereo mixer (constant-power panning), OscillatorBank multi-layer rendering with tests
+- [ ] 02-03-PLAN.md — MP3 encoder package, zero-packet guard, -o CLI flag, ffprobe integration test
 
 ### Phase 3: Pipeline Integration and MVP
 **Goal**: Live capture flows end-to-end into audio synthesis — the complete v1 MVP: run, capture, Ctrl+C, get an MP3
@@ -78,6 +82,6 @@ Phases execute in numeric order: 1 → 2 → 3 → 4
 | Phase | Plans Complete | Status | Completed |
 |-------|----------------|--------|-----------|
 | 1. Capture and Classification | 4/4 | Complete   | 2026-03-25 |
-| 2. Audio Synthesis Engine | 0/? | Not started | - |
+| 2. Audio Synthesis Engine | 0/3 | Planning complete | - |
 | 3. Pipeline Integration and MVP | 0/? | Not started | - |
 | 4. Power User Features | 0/? | Not started | - |