feat: agent coordination system (workflows, locks, components, messages)

Adds /api/coord/* endpoints for real-time cross-session coordination:
- coord_workflows: named units of work per project
- coord_work_items: tasks within workflows with dependency chains
- coord_session_locks: exclusive resource locks with auto-expiry (TTL)
- coord_component_states: live component state per project (upsert)
- coord_messages: cross-session messaging and broadcasts
- /api/coord/status: cross-project snapshot endpoint

Replaces PROJECT_STATE.md as the coordination layer for Claude sessions.

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

api/models/__init__.py

@@ -5,6 +5,11 @@ This package contains all database models and their base classes.
 """
 
 from api.models.api_audit_log import ApiAuditLog
+from api.models.coord_workflow import CoordWorkflow
+from api.models.coord_work_item import CoordWorkItem
+from api.models.coord_session_lock import CoordSessionLock
+from api.models.coord_component_state import CoordComponentState
+from api.models.coord_message import CoordMessage
 from api.models.backup_log import BackupLog
 from api.models.base import Base, TimestampMixin, UUIDMixin
 from api.models.billable_time import BillableTime
@@ -47,6 +52,11 @@ from api.models.work_item_tag import WorkItemTag
 
 __all__ = [
     "ApiAuditLog",
+    "CoordWorkflow",
+    "CoordWorkItem",
+    "CoordSessionLock",
+    "CoordComponentState",
+    "CoordMessage",
     "BackupLog",
     "Base",
     "BillableTime",