feat: add skills and subagents configuration support

- Updated .gitignore to include skills directory.
- Introduced agent discovery functionality to scan for AGENT.md files in user and project directories.
- Added new API endpoint for discovering filesystem agents.
- Implemented UI components for managing skills and viewing custom subagents.
- Enhanced settings helpers to retrieve skills configuration and custom subagents.
- Updated agent service to incorporate skills and subagents in task delegation.

These changes enhance the capabilities of the system by allowing users to define and manage skills and custom subagents effectively.

apps/ui/src/lib/http-api-client.ts

@@ -23,8 +23,6 @@ import type {
   SpecRegenerationEvent,
   SuggestionType,
   GitHubAPI,
-  GitHubIssue,
-  GitHubPR,
   IssueValidationInput,
   IssueValidationEvent,
   IdeationAPI,
@@ -1677,6 +1675,26 @@ export class HttpApiClient implements ElectronAPI {
       migratedProjectCount: number;
       errors: string[];
     }> => this.post('/api/settings/migrate', { data }),
+
+    // Filesystem agents discovery (read-only)
+    discoverAgents: (
+      projectPath?: string,
+      sources?: Array<'user' | 'project'>
+    ): Promise<{
+      success: boolean;
+      agents?: Array<{
+        name: string;
+        definition: {
+          description: string;
+          prompt: string;
+          tools?: string[];
+          model?: 'sonnet' | 'opus' | 'haiku' | 'inherit';
+        };
+        source: 'user' | 'project';
+        filePath: string;
+      }>;
+      error?: string;
+    }> => this.post('/api/settings/agents/discover', { projectPath, sources }),
   };
 
   // Sessions API