docs(05-04): complete mouse play/pause WS fix plan — SUMMARY, STATE, ROADMAP updated

- 05-04-SUMMARY.md: gap closure complete, UDP cues fire for mouse playback
- STATE.md: plan advanced to 2/4, progress 100%, decision logged
- ROADMAP.md: Phase 05 marked Complete (4/4 plans)

.planning/ROADMAP.md

@@ -112,7 +112,7 @@ Plans:
 - [x] 05-01-PLAN.md — Cue scheduler: server-side position-driven scheduling, 60ms look-ahead, seek-safe fired_ids reset
 - [x] 05-02-PLAN.md — Live preview panel + show selector: DOM device strips, preview_update handler, show load into timeline
 - [x] 05-03-PLAN.md — Keyboard shortcuts: Space, arrows, Ctrl+Z/Y/S for mouse-free operation
-- [ ] 05-04-PLAN.md — Gap closure: wire WebSocket play/pause messages from mouse transport button
+- [x] 05-04-PLAN.md — Gap closure: wire WebSocket play/pause messages from mouse transport button
 **UI hint**: yes
 
 ### Phase 6: AI Sync
@@ -157,6 +157,6 @@ Phases execute in numeric order: 1 → 2 → 3 → 4 → 5 → 6 → 7
 | 2. Audio Engine | 3/3 | Complete   | 2026-04-06 |
 | 3. Communication Protocol | 3/3 | Complete   | 2026-04-06 |
 | 4. Timeline Editor | 4/4 | Complete   | 2026-04-06 |
-| 5. Live Show Execution | 3/3 | Complete   | 2026-04-07 |
+| 5. Live Show Execution | 4/4 | Complete   | 2026-04-07 |
 | 6. AI Sync | 0/3 | Not started | - |
 | 7. Microcontroller Firmware | 0/3 | Not started | - |