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/api/__init__.py

@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+"""
+API Routes Package
+
+Provides REST API endpoints for:
+- Agent management
+- Workspace management
+- Tool guard operations
+"""
+
+from .agents import router as agents_router
+from .workspaces import router as workspaces_router
+from .guard import router as guard_router
+from .runtime import router as runtime_router
+
+__all__ = [
+    "agents_router",
+    "workspaces_router",
+    "guard_router",
+    "runtime_router",
+]