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/services/coord_work_item_service.py

@@ -0,0 +1,100 @@
+"""Service layer for CoordWorkItem."""
+
+from typing import Optional
+from uuid import UUID
+
+from fastapi import HTTPException, status
+from sqlalchemy.orm import Session
+
+from api.models.coord_work_item import CoordWorkItem
+from api.models.coord_workflow import CoordWorkflow
+from api.schemas.coord_work_item import CoordWorkItemCreate, CoordWorkItemUpdate
+
+
+def get_work_items(
+    db: Session,
+    workflow_id: Optional[str] = None,
+    project_key: Optional[str] = None,
+    status_filter: Optional[str] = None,
+    assigned_session: Optional[str] = None,
+    skip: int = 0,
+    limit: int = 100,
+) -> tuple[list[CoordWorkItem], int]:
+    """Return paginated work items with optional filters."""
+    q = db.query(CoordWorkItem)
+    if workflow_id:
+        q = q.filter(CoordWorkItem.workflow_id == workflow_id)
+    if project_key:
+        q = q.filter(CoordWorkItem.project_key == project_key)
+    if status_filter:
+        q = q.filter(CoordWorkItem.status == status_filter)
+    if assigned_session:
+        q = q.filter(CoordWorkItem.assigned_session == assigned_session)
+    total = q.count()
+    items = q.order_by(CoordWorkItem.priority.desc(), CoordWorkItem.created_at.asc()).offset(skip).limit(limit).all()
+    return items, total
+
+
+def get_work_item_by_id(db: Session, item_id: UUID) -> CoordWorkItem:
+    """Return a single work item or raise 404."""
+    item = db.query(CoordWorkItem).filter(CoordWorkItem.id == str(item_id)).first()
+    if not item:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Work item {item_id} not found"
+        )
+    return item
+
+
+def create_work_item(db: Session, data: CoordWorkItemCreate) -> CoordWorkItem:
+    """Create and persist a new work item, validating the parent workflow exists."""
+    workflow = db.query(CoordWorkflow).filter(CoordWorkflow.id == data.workflow_id).first()
+    if not workflow:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Workflow {data.workflow_id} not found"
+        )
+    try:
+        item = CoordWorkItem(**data.model_dump())
+        db.add(item)
+        db.commit()
+        db.refresh(item)
+        return item
+    except Exception as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            detail=f"Failed to create work item: {e}"
+        )
+
+
+def update_work_item(db: Session, item_id: UUID, data: CoordWorkItemUpdate) -> CoordWorkItem:
+    """Apply partial update to a work item."""
+    item = get_work_item_by_id(db, item_id)
+    try:
+        for field, value in data.model_dump(exclude_unset=True).items():
+            setattr(item, field, value)
+        db.commit()
+        db.refresh(item)
+        return item
+    except Exception as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            detail=f"Failed to update work item: {e}"
+        )
+
+
+def delete_work_item(db: Session, item_id: UUID) -> dict:
+    """Delete a work item by ID."""
+    item = get_work_item_by_id(db, item_id)
+    try:
+        db.delete(item)
+        db.commit()
+        return {"message": "Work item deleted", "item_id": str(item_id)}
+    except Exception as e:
+        db.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            detail=f"Failed to delete work item: {e}"
+        )