feat: add Discuss and Explore subagents for dynamic critique and code exploration

- Implement Discuss Subagent for multi-perspective critique with dynamic perspectives.
- Create Explore Subagent for shared codebase exploration with centralized caching.
- Add tests for CcwToolsMcpCard component to ensure enabled tools are preserved on config save.
- Introduce SessionPreviewPanel component for previewing and selecting sessions for Memory V2 extraction.
- Develop CommandCreateDialog component for creating/importing commands with import and CLI generate modes.

ccw/frontend/src/locales/en/mcp-manager.json

@@ -169,6 +169,10 @@
       "saveConfig": "Save Configuration",
       "saving": "Saving..."
     },
+    "feedback": {
+      "saveSuccess": "Configuration saved",
+      "saveError": "Failed to save configuration"
+    },
     "scope": {
       "global": "Global",
       "project": "Project",