docs(09-01): complete outbox drain trigger wiring plan

.planning/REQUIREMENTS.md

@@ -14,7 +14,7 @@ Each requirement maps to exactly one roadmap phase (see Traceability).
 
 - [ ] **CAL-13**: User can choose a reminder lead time when creating or editing an event from a preset list (None / 5m / 10m / 15m / 30m / 1h / 2h / 1d / 2d), with **"None" as the default**; the choice is serialized as a VALARM on the event written back to Fastmail.
 - [ ] **CAL-14**: Editing an event **preserves any existing reminder/VALARM** set in another client (Fastmail or native) — reminders are never silently stripped on round-trip.
-- [ ] **CAL-15**: A created, edited, or deleted event reaches Fastmail within ~2 seconds (event-driven outbox drain) instead of up to ~15s, while preserving the optimistic-202 accept and all outbox durability guarantees (create-before-delete ordering, drain concurrency guard, fresh-etag-before-PUT, per-uid exactly-once).
+- [x] **CAL-15**: A created, edited, or deleted event reaches Fastmail within ~2 seconds (event-driven outbox drain) instead of up to ~15s, while preserving the optimistic-202 accept and all outbox durability guarantees (create-before-delete ordering, drain concurrency guard, fresh-etag-before-PUT, per-uid exactly-once).
 
 ### Notifications — Variable-lead reminder scheduling
 
@@ -75,7 +75,7 @@ Maps each REQ-ID to its phase. v1.1 phases continue v1.0 numbering (v1.0 ended a
 | TEST-02  | Phase 7 (Mobile Test Harness)    | Complete |
 | CI-01    | Phase 8 (Gitea CI)               | Complete |
 | CI-02    | Phase 8 (Gitea CI)               | Complete |
-| CAL-15   | Phase 9 (Faster Write-Back)      | Pending  |
+| CAL-15   | Phase 9 (Faster Write-Back)      | Complete |
 | ADMIN-01 | Phase 10 (Admin Role & Settings) | Pending  |
 | ADMIN-02 | Phase 10 (Admin Role & Settings) | Pending  |
 | ADMIN-03 | Phase 10 (Admin Role & Settings) | Pending  |