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/__init__.py

@@ -0,0 +1,13 @@
+from .agent_runtime import AgentRuntimeState
+from .context import TradingRunContext
+from .manager import TradingRuntimeManager
+from .registry import RuntimeRegistry
+from .session import TradingSessionKey
+
+__all__ = [
+    "AgentRuntimeState",
+    "TradingRunContext",
+    "TradingRuntimeManager",
+    "RuntimeRegistry",
+    "TradingSessionKey",
+]