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/agents/workspace_manager.py

@@ -9,7 +9,7 @@ import yaml
 from .skills_manager import SkillsManager
 
 
-class WorkspaceManager:
+class RunWorkspaceManager:
     """Create and maintain run-level prompt asset files for each agent."""
 
     def __init__(self, project_root: Optional[Path] = None):
@@ -197,3 +197,7 @@ class WorkspaceManager:
             yaml.safe_dump(payload, allow_unicode=True, sort_keys=False),
             encoding="utf-8",
         )
+
+
+# Backward-compatible alias: code importing WorkspaceManager from this module should continue to work.
+WorkspaceManager = RunWorkspaceManager