chore(workplan): split WP-0003 into three context-window-sized parts

WP-0003 (24 tasks) exceeds the single-run limit. Split by build phase:
  0003a — phases 7–8: domain model, rules module, IssueSink, event type registry (10 tasks)
  0003b — phases 9–10: ActivityDefinition parser, workflow wiring, triggers, webhooks (7 tasks)
  0003c — phases 11–12: context adapters, first ActivityDefinition, test suite (7 tasks)

Original WP-0003 marked superseded. Hub task IDs and workstream ID unchanged.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

workplans/custodian-WP-0003-event-bridge.md

@@ -3,7 +3,11 @@ id: custodian-WP-0003
 type: workplan
 domain: custodian
 repo: activity-core
-status: active
+status: superseded
+superseded_by:
+  - custodian-WP-0003a   # phases 7–8: model, rules, registry
+  - custodian-WP-0003b   # phases 9–10: parser, workflow, triggers, webhooks
+  - custodian-WP-0003c   # phases 11–12: context adapters, integration
 state_hub_workstream_id: b4eb45a9-69e3-4ab0-b00c-67a53c3117c5
 depends_on:
   - custodian-WP-0001   # Foundation — Temporal Backbone