feat: auto-create Integration phase for multi-leaf initiatives

When an initiative has multiple end phases (leaf nodes with no
dependents), queueAllPhases now auto-creates an Integration phase
that depends on all of them. This catches cross-phase incompatibilities
(type mismatches, conflicting exports, broken tests) before review.

docs/dispatch-events.md

@@ -93,6 +93,18 @@ InitiativeChangesRequestedEvent { initiativeId, phaseId, taskId }
 4. **Auto-queue tasks** — When phase starts (branches confirmed), pending execution tasks are queued (planning-category tasks excluded)
 5. **Events** — `phase:queued`, `phase:started`, `phase:completed`, `phase:blocked`
 
+### Auto-Integration Phase
+
+When `queueAllPhases` is called (i.e. the user clicks "Execute"), it auto-creates an **Integration** phase if the initiative has multiple end phases (leaf nodes with no dependents). This catches cross-phase incompatibilities before the initiative reaches review.
+
+- **Trigger**: `queueAllPhases` in `apps/server/trpc/routers/phase-dispatch.ts`
+- **Guard**: Only created when `endPhaseIds.length > 1` and no existing "Integration" phase
+- **Status**: Created as `approved` (same pattern as Finalization in orchestrator.ts)
+- **Dependencies**: Integration depends on all end phases — dispatched last
+- **Task**: A single `verify` category task instructs the agent to build, run tests, check types, and review cross-phase imports
+- **Idempotency**: Name-based check prevents duplicates on re-execution
+- **Coexistence**: Independent of the Finalization phase (different purpose, different trigger)
+
 ### PhaseDispatchManager Methods
 
 | Method | Purpose |