docs(01-04): complete typing exercise engine plan

- SUMMARY.md with 2 task commits, 18 tests, 6 files
- STATE.md: advance to plan 5/5, 80% progress
- ROADMAP.md: update phase 01 plan progress
- REQUIREMENTS.md: mark TYPE-01..04, LEVL-02, LEVL-03 complete

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.planning/STATE.md

@@ -3,14 +3,14 @@ gsd_state_version: 1.0
 milestone: v1.0
 milestone_name: milestone
 status: executing
-stopped_at: Completed 01-03-PLAN.md
-last_updated: "2026-03-29T09:08:47.424Z"
+stopped_at: Completed 01-04-PLAN.md
+last_updated: "2026-03-29T09:13:14.395Z"
 last_activity: 2026-03-29
 progress:
   total_phases: 4
   completed_phases: 0
   total_plans: 5
-  completed_plans: 3
+  completed_plans: 4
   percent: 0
 ---
 
@@ -26,7 +26,7 @@ See: .planning/PROJECT.md (updated 2026-03-29)
 ## Current Position
 
 Phase: 01 (grundger-st-tippmechanik) — EXECUTING
-Plan: 4 of 5
+Plan: 5 of 5
 Status: Ready to execute
 Last activity: 2026-03-29
 
@@ -55,6 +55,7 @@ Progress: [░░░░░░░░░░] 0%
 | Phase 01 P01 | 4min | 2 tasks | 22 files |
 | Phase 01 P02 | 2min | 2 tasks | 6 files |
 | Phase 01 P03 | 3min | 2 tasks | 4 files |
+| Phase 01 P04 | 2min | 2 tasks | 6 files |
 
 ## Accumulated Context
 
@@ -70,6 +71,7 @@ Recent decisions affecting current work:
 - [Phase 01]: Screen transitions use CSS opacity+display toggle, no router library
 - [Phase 01]: Companion cards rendered dynamically from data array, not hardcoded HTML
 - [Phase 01]: Finger color map duplicated in keyboard.ts for module independence
+- [Phase 01]: Exercise state uses direct mutation pattern for game loop simplicity
 
 ### Pending Todos
 
@@ -81,6 +83,6 @@ None yet.
 
 ## Session Continuity
 
-Last session: 2026-03-29T09:08:47.417Z
-Stopped at: Completed 01-03-PLAN.md
+Last session: 2026-03-29T09:13:14.388Z
+Stopped at: Completed 01-04-PLAN.md
 Resume file: None