feat: Add agent workspace system and runtime management

- Add agent core modules (agent_core, factory, registry, skill_loader)
- Add runtime system for agent execution management
- Add REST API for agents, workspaces, and runtime control
- Add process supervisor for agent lifecycle management
- Add workspace template system with agent profiles
- Add frontend RuntimeView and runtime API integration
- Add per-agent skill workspaces for smoke_fullstack run
- Refactor skill system with active/installed separation

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

backend/runtime/agent_runtime.py

@@ -0,0 +1,26 @@
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from datetime import datetime, UTC
+from typing import Any, Dict
+
+
+@dataclass
+class AgentRuntimeState:
+    agent_id: str
+    status: str = "idle"
+    last_session: str | None = None
+    last_updated: datetime = field(default_factory=lambda: datetime.now(UTC))
+
+    def update(self, status: str, session_key: str | None = None) -> None:
+        self.status = status
+        self.last_session = session_key
+        self.last_updated = datetime.now(UTC)
+
+    def to_dict(self) -> Dict[str, Any]:
+        return {
+            "agent_id": self.agent_id,
+            "status": self.status,
+            "last_session": self.last_session,
+            "last_updated": self.last_updated.isoformat(),
+        }