docs(02-02): complete OscillatorBank and stereo mixer plan

- Created 02-02-SUMMARY.md with plan results and 14 test descriptions
- Updated STATE.md: advanced to plan 3 of 3, recorded metrics and decisions
- Updated ROADMAP.md: phase 02 showing 2/3 summaries complete
- Marked SYNTH-03 complete in REQUIREMENTS.md

.planning/STATE.md

@@ -3,13 +3,13 @@ gsd_state_version: 1.0
 milestone: v1.0
 milestone_name: milestone
 status: Ready to execute
-stopped_at: "Completed 02-01: synth config, oscillator, and layer"
-last_updated: "2026-03-26T10:59:51.259Z"
+stopped_at: "Completed 02-02: OscillatorBank and stereo mixer"
+last_updated: "2026-03-26T11:04:17.995Z"
 progress:
   total_phases: 4
   completed_phases: 1
   total_plans: 7
-  completed_plans: 4
+  completed_plans: 6
 ---
 
 # Project State
@@ -24,7 +24,7 @@ See: .planning/PROJECT.md (updated 2026-03-24)
 ## Current Position
 
 Phase: 02 (audio-synthesis-engine) — EXECUTING
-Plan: 2 of 3
+Plan: 3 of 3
 
 ## Performance Metrics
 
@@ -51,6 +51,7 @@ Plan: 2 of 3
 | Phase 01-capture-and-classification P02 | 3min | 1 tasks | 4 files |
 | Phase 01-capture-and-classification P04 | 15min | 2 tasks | 2 files |
 | Phase 02 P01 | 15min | 2 tasks | 8 files |
+| Phase 02 P02 | 10min | 2 tasks | 4 files |
 
 ## Accumulated Context
 
@@ -76,6 +77,8 @@ Recent decisions affecting current work:
 - [Phase 01-04]: Three-stage pipeline: capture -> classify goroutine -> aggregate via buffered channels; 1024-buffered classified channel absorbs burst processing
 - [Phase 02]: go-lame v0.0.9 used for MP3 encoding (embedded LAME C source, no system library needed)
 - [Phase 02]: go-audio/wav excluded — writing PCM bytes directly to LameWriter is simpler (per Claude's Discretion grant in CONTEXT.md)
+- [Phase 02]: GainPerLayer applied in bank.go during mixing to ensure 11 max layers sum to 1.0 (D-10)
+- [Phase 02]: int16 conversion uses float * 32767 to avoid positive overflow at exactly +1.0
 
 ### Pending Todos
 
@@ -89,6 +92,6 @@ None yet.
 
 ## Session Continuity
 
-Last session: 2026-03-26T10:59:51.252Z
-Stopped at: Completed 02-01: synth config, oscillator, and layer
+Last session: 2026-03-26T11:04:17.988Z
+Stopped at: Completed 02-02: OscillatorBank and stereo mixer
 Resume file: None