docs(18-04): create initiative detail page assembly summary and update state

Phase 18 (Initiative Detail) complete — all 4 plans finished.

.planning/STATE.md

@@ -9,19 +9,19 @@ See: .planning/PROJECT.md (updated 2026-02-04)
 
 ## Current Position
 
-Phase: 18 of 21 (Initiative Detail)
-Plan: 3 of 4 in current phase
-Status: In progress
-Last activity: 2026-02-04 - Completed 18-03-PLAN.md
+Phase: 18 of 21 (Initiative Detail) - COMPLETE
+Plan: 4 of 4 in current phase
+Status: Phase complete
+Last activity: 2026-02-04 - Completed 18-04-PLAN.md (Initiative Detail page assembly)
 
-Progress: █████████░ 97%
+Progress: █████████░ 98%
 
 ## Performance Metrics
 
 **Velocity:**
-- Total plans completed: 68
+- Total plans completed: 69
 - Average duration: 3 min
-- Total execution time: 191 min
+- Total execution time: 195 min
 
 **By Phase (v1.0):**
 
@@ -208,6 +208,11 @@ Recent decisions affecting current work:
 - 18-02: Underscore prefix for unused type prop in DependencyIndicator (_type) to satisfy noUnusedParameters
 - 18-03: SerializedTask type mirrors SerializedInitiative pattern (Date fields become string over JSON)
 - 18-03: Both DecisionList and TaskDetailModal are purely presentational with callback props (no tRPC calls inside)
+- 18-04: PhaseWithTasks helper component pattern solves hooks-in-loops problem for nested data fetching
+- 18-04: PlanTasksFetcher renders null — data-only component for per-plan task fetching with stable hook count
+- 18-04: Task counts aggregated via callback from PhaseWithTasks to page-level state
+- 18-04: DecisionList passed empty array — no backend endpoint for decisions yet
+- 18-04: Phase/task dependencies simplified (empty arrays) for v1 — full dependency resolution deferred
 
 ### Pending Todos
 
@@ -230,5 +235,5 @@ None.
 ## Session Continuity
 
 Last session: 2026-02-04
-Stopped at: Completed 18-03-PLAN.md
+Stopped at: Completed Phase 18 (Initiative Detail) - all 4 plans done
 Resume file: None