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/coord_workflow.py

@@ -0,0 +1,61 @@
+"""Coordination workflow model."""
+
+from datetime import datetime
+from typing import Optional
+
+from sqlalchemy import CHAR, CheckConstraint, Index, String, Text, DateTime
+from sqlalchemy.orm import Mapped, mapped_column
+
+from .base import Base, TimestampMixin, UUIDMixin
+
+
+class CoordWorkflow(Base, UUIDMixin, TimestampMixin):
+    """A named unit of work spanning one or more sessions."""
+
+    __tablename__ = "coord_workflows"
+
+    project_key: Mapped[str] = mapped_column(
+        String(200),
+        nullable=False,
+        doc="Project namespace slug, e.g. 'gururmm', 'client/acme-corp'"
+    )
+
+    name: Mapped[str] = mapped_column(
+        String(200),
+        nullable=False,
+        doc="Short identifier, e.g. 'discovery-feature'"
+    )
+
+    description: Mapped[Optional[str]] = mapped_column(
+        Text,
+        doc="Freeform description, markdown ok"
+    )
+
+    status: Mapped[str] = mapped_column(
+        String(20),
+        nullable=False,
+        default="planning",
+        doc="Status: planning, active, blocked, completed, cancelled"
+    )
+
+    created_by: Mapped[str] = mapped_column(
+        String(200),
+        nullable=False,
+        doc="Session that created this workflow, e.g. 'DESKTOP-0O8A1RL/Claude'"
+    )
+
+    completed_at: Mapped[Optional[datetime]] = mapped_column(
+        DateTime,
+        doc="When the workflow reached a terminal state"
+    )
+
+    __table_args__ = (
+        CheckConstraint(
+            "status IN ('planning', 'active', 'blocked', 'completed', 'cancelled')",
+            name="ck_coord_workflows_status"
+        ),
+        Index("idx_coord_workflows_project_status", "project_key", "status"),
+    )
+
+    def __repr__(self) -> str:
+        return f"<CoordWorkflow(project_key='{self.project_key}', name='{self.name}', status='{self.status}')>"