docs(12-08): complete TestHarness helpers & decompose E2E tests plan

Tasks completed: 2/2
- Add TestHarness decompose mode helpers
- Add decompose mode E2E tests

Phase 12 complete (8/8 plans).

SUMMARY: .planning/phases/12-phase-task-decomposition/12-08-SUMMARY.md

.planning/STATE.md

@@ -10,18 +10,18 @@ See: .planning/PROJECT.md (updated 2026-01-31)
 ## Current Position
 
 Phase: 12 of 13 (Phase Task Decomposition)
-Plan: 7 of 8 in current phase
-Status: In progress
-Last activity: 2026-02-01 — Completed 12-07-PLAN.md
+Plan: 8 of 8 in current phase
+Status: Phase complete
+Last activity: 2026-02-01 — Completed 12-08-PLAN.md
 
-Progress: ███████░░░ 75%
+Progress: █████████░ 92%
 
 ## Performance Metrics
 
 **Velocity:**
-- Total plans completed: 48
+- Total plans completed: 49
 - Average duration: 3 min
-- Total execution time: 154 min
+- Total execution time: 158 min
 
 **By Phase (v1.0):**
 
@@ -156,6 +156,9 @@ Recent decisions affecting current work:
 - 12-05: spawnArchitectDecompose associates with planId (not initiativeId) matching decompose scope
 - 12-06: Architect decompose added as subcommand under existing architect group (consistent with discuss/breakdown)
 - 12-06: Plan commands follow same pattern as initiative commands for consistency
+- 12-08: planRepository added to harness for plan operations in E2E tests
+- 12-08: Decompose helpers follow same pattern as architect discuss/breakdown helpers
+- 12-08: Agent waiting emits agent:waiting event, not agent:stopped (Q&A flow)
 
 ### Pending Todos
 
@@ -176,5 +179,5 @@ None.
 ## Session Continuity
 
 Last session: 2026-02-01
-Stopped at: Completed 12-07-PLAN.md (Unit Tests for Decompose Mode & PlanRepository)
+Stopped at: Completed 12-08-PLAN.md (TestHarness Helpers & Decompose E2E Tests)
 Resume file: None