feat: Add MCP search server toggle with dedicated API architecture (#85)

* feat: add MCP search server toggle functionality

- Introduced `CLAUDE_MEM_MCP_ENABLED` setting to manage the MCP search server state.
- Updated `WorkerService` to handle MCP enabling/disabling based on the new setting.
- Enhanced `Sidebar` component to include a checkbox for toggling MCP search server.
- Modified `useSettings` hook to incorporate the new MCP setting.
- Updated default settings to include `CLAUDE_MEM_MCP_ENABLED` with a default value of true.
- Adjusted TypeScript types to include the new MCP setting.

* feat: Implement MCP toggle functionality in WorkerService and Sidebar

- Added API endpoints for MCP status retrieval and toggling in WorkerService.
- Updated Sidebar component to manage MCP toggle state and display status messages.
- Removed MCP_ENABLED from settings state management and default settings.
- Adjusted settings interface and related hooks to reflect the removal of MCP_ENABLED.

src/services/worker-service.ts

@@ -14,7 +14,7 @@ import express, { Request, Response } from 'express';
 import cors from 'cors';
 import http from 'http';
 import path from 'path';
-import { readFileSync, writeFileSync, statSync, existsSync } from 'fs';
+import { readFileSync, writeFileSync, statSync, existsSync, renameSync } from 'fs';
 import { homedir } from 'os';
 import { getPackageRoot } from '../shared/paths.js';
 import { getWorkerPort } from '../shared/worker-utils.js';
@@ -101,6 +101,10 @@ export class WorkerService {
     this.app.get('/api/settings', this.handleGetSettings.bind(this));
     this.app.post('/api/settings', this.handleUpdateSettings.bind(this));
 
+    // MCP toggle
+    this.app.get('/api/mcp/status', this.handleGetMcpStatus.bind(this));
+    this.app.post('/api/mcp/toggle', this.handleToggleMcp.bind(this));
+
     // Search API endpoints (for skill-based search)
     this.app.get('/api/search/observations', this.handleSearchObservations.bind(this));
     this.app.get('/api/search/sessions', this.handleSearchSessions.bind(this));
@@ -655,6 +659,83 @@ export class WorkerService {
     }
   }
 
+  // ============================================================================
+  // MCP Toggle Handlers
+  // ============================================================================
+
+  /**
+   * GET /api/mcp/status - Check if MCP search server is enabled
+   */
+  private handleGetMcpStatus(req: Request, res: Response): void {
+    try {
+      const enabled = this.isMcpEnabled();
+      res.json({ enabled });
+    } catch (error) {
+      logger.failure('WORKER', 'Get MCP status failed', {}, error as Error);
+      res.status(500).json({ error: (error as Error).message });
+    }
+  }
+
+  /**
+   * POST /api/mcp/toggle - Toggle MCP search server on/off
+   * Body: { enabled: boolean }
+   */
+  private handleToggleMcp(req: Request, res: Response): void {
+    try {
+      const { enabled } = req.body;
+
+      if (typeof enabled !== 'boolean') {
+        res.status(400).json({ error: 'enabled must be a boolean' });
+        return;
+      }
+
+      this.toggleMcp(enabled);
+      res.json({ success: true, enabled: this.isMcpEnabled() });
+    } catch (error) {
+      logger.failure('WORKER', 'Toggle MCP failed', {}, error as Error);
+      res.status(500).json({ success: false, error: (error as Error).message });
+    }
+  }
+
+  // ============================================================================
+  // MCP Toggle Helpers
+  // ============================================================================
+
+  /**
+   * Check if MCP search server is enabled
+   */
+  private isMcpEnabled(): boolean {
+    const packageRoot = getPackageRoot();
+    const mcpPath = path.join(packageRoot, 'plugin', '.mcp.json');
+    return existsSync(mcpPath);
+  }
+
+  /**
+   * Toggle MCP search server (rename .mcp.json <-> .mcp.json.disabled)
+   */
+  private toggleMcp(enabled: boolean): void {
+    try {
+      const packageRoot = getPackageRoot();
+      const mcpPath = path.join(packageRoot, 'plugin', '.mcp.json');
+      const mcpDisabledPath = path.join(packageRoot, 'plugin', '.mcp.json.disabled');
+
+      if (enabled && existsSync(mcpDisabledPath)) {
+        // Enable: rename .mcp.json.disabled -> .mcp.json
+        renameSync(mcpDisabledPath, mcpPath);
+        logger.info('WORKER', 'MCP search server enabled');
+      } else if (!enabled && existsSync(mcpPath)) {
+        // Disable: rename .mcp.json -> .mcp.json.disabled
+        renameSync(mcpPath, mcpDisabledPath);
+        logger.info('WORKER', 'MCP search server disabled');
+      } else {
+        logger.debug('WORKER', 'MCP toggle no-op (already in desired state)', { enabled });
+      }
+    } catch (error) {
+      logger.failure('WORKER', 'Failed to toggle MCP', { enabled }, error as Error);
+      throw error;
+    }
+  }
+
   // ============================================================================
   // Search API Handlers (for skill-based search)
   // ============================================================================