docs(18-03): create summary and update state for DecisionList/TaskDetailModal plan

.planning/phases/18-initiative-detail/18-03-SUMMARY.md

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+# Plan 18-03 Summary
+
+## Result: COMPLETE
+
+**Tasks:** 2/2 completed
+**Duration:** ~3 min
+
+## What was built
+
+### DecisionList component
+- Collapsible list of key decisions in a Card with "Key Decisions" header
+- Each decision individually expandable with ChevronDown/ChevronRight indicators
+- Internal state tracks expanded indices via `Set<number>`
+- Show more/less button when decisions exceed `maxVisible` (default 3)
+- Empty state placeholder: "No decisions recorded"
+- File: `packages/web/src/components/DecisionList.tsx`
+
+### TaskDetailModal component
+- Controlled Dialog (open when `task !== null`) following CreateInitiativeDialog pattern
+- Metadata grid: Status (StatusBadge), Priority, Phase, Type, Agent
+- Description section with fallback to "No description"
+- Dependencies section listing dependency names with status badges
+- Blocks section listing dependent names with status badges
+- Queue Task button: enabled only when status is 'pending' and all dependencies completed
+- Stop Task button: enabled only when status is 'in_progress'
+- SerializedTask interface for tRPC Date-to-string wire format
+- File: `packages/web/src/components/TaskDetailModal.tsx`
+
+## Decisions
+
+- 18-03: SerializedTask type mirrors SerializedInitiative pattern (Date fields become string over JSON)
+- 18-03: Both components are purely presentational with callback props (no tRPC calls inside)
+
+## Commits
+
+- `3baba49`: feat(18-03): create DecisionList component for initiative detail
+- `5b17b7a`: feat(18-03): create TaskDetailModal component for initiative detail
+
+## Verification
+
+- [x] `npx tsc --noEmit -p packages/web/tsconfig.app.json` passes
+- [x] `npx vite build` in packages/web succeeds
+- [x] Both components export correctly
+- [x] Dialog follows controlled pattern matching CreateInitiativeDialog