Implement terminal approval UI system

Phase 1: Backend approval tracking
- Add PendingApprovalsManager class to track pending approvals
- Add approval-request, approval-response, approval-expired WebSocket handlers
- Add requestApproval() method to ClaudeCodeService
- Add event forwarding for approval requests

Phase 2: Frontend approval card component
- Create approval-card.js with interactive UI
- Create approval-card.css with styled component
- Add Approve, Custom Instructions, Reject buttons
- Add expandable custom command input

Phase 3: Wire up approval flow end-to-end
- Add handleApprovalRequest, handleApprovalConfirmed, handleApprovalExpired handlers
- Add detectApprovalRequest() to parse AI approval request patterns
- Integrate approval card into WebSocket message flow
- Route approval responses based on source (server vs AI conversational)

This allows the AI agent to request command approval through a clean
UI instead of confusing conversational text responses.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

services/claude-service.js

@@ -293,6 +293,38 @@ class ClaudeCodeService extends EventEmitter {
     return { success: true };
   }
 
+  /**
+   * Request approval for a command (instead of executing directly)
+   * @param {string} sessionId - Session ID
+   * @param {string} command - Command requiring approval
+   * @param {string} explanation - Human-readable explanation of what will happen
+   */
+  requestApproval(sessionId, command, explanation) {
+    const session = this.sessions.get(sessionId);
+
+    if (!session) {
+      throw new Error(`Session ${sessionId} not found`);
+    }
+
+    console.log(`[ClaudeService] Requesting approval for session ${sessionId}:`, command);
+
+    // Track the pending request in session context
+    session.context.messages.push({
+      role: 'system',
+      content: `[AWAITING APPROVAL: ${command}]`,
+      timestamp: new Date().toISOString()
+    });
+
+    // Emit approval-request event for WebSocket to handle
+    this.emit('approval-request', {
+      sessionId,
+      command,
+      explanation
+    });
+
+    return { success: true, awaitingApproval: true };
+  }
+
   /**
    * Get session details (handles both active and historical sessions)
    */