Implement systemd service approach for nixos-rebuild operations

- Add cm-rebuild systemd service for process isolation
- Add sudo permissions for service control and journal access
- Remove verbose flag for cleaner output
- Ensures reliable rebuild operations without agent crashes

CLAUDE.md

@@ -92,6 +92,56 @@ Storage:
 - ✅ **Git Clone Approach**: Implemented for nixos-rebuild to avoid directory permissions
 - ✅ **Visual Feedback**: Directional arrows for service status (↑ starting, ↓ stopping, ↻ restarting)
 
+### Terminal Popup for Real-time Output - IMPLEMENTED ✅
+
+**Status (as of 2025-10-26):**
+- ✅ **Terminal Popup UI**: 80% screen coverage with terminal styling and color-coded output
+- ✅ **ZMQ Streaming Protocol**: CommandOutputMessage for real-time output transmission
+- ✅ **Keyboard Controls**: ESC/Q to close, ↑↓ to scroll, manual close (no auto-close)
+- ✅ **Real-time Display**: Live streaming of command output as it happens
+- ✅ **Version-based Agent Reporting**: Shows "Agent: v0.1.13" instead of nix store hash
+
+**Current Implementation Issues:**
+- ❌ **Agent Process Crashes**: Agent dies during nixos-rebuild execution
+- ❌ **Inconsistent Output**: Different outputs each time 'R' is pressed
+- ❌ **Limited Output Visibility**: Not capturing all nixos-rebuild progress
+
+**PLANNED SOLUTION - Systemd Service Approach:**
+
+**Problem**: Direct nixos-rebuild execution in agent causes process crashes and inconsistent output.
+
+**Solution**: Create dedicated systemd service for rebuild operations.
+
+**Implementation Plan:**
+1. **NixOS Systemd Service**:
+   ```nix
+   systemd.services.cm-rebuild = {
+     description = "CM Dashboard NixOS Rebuild";
+     serviceConfig = {
+       Type = "oneshot";
+       ExecStart = "${pkgs.nixos-rebuild}/bin/nixos-rebuild switch --flake . --option sandbox false";
+       WorkingDirectory = "/var/lib/cm-dashboard/nixos-config";
+       User = "root";
+       StandardOutput = "journal";
+       StandardError = "journal";
+     };
+   };
+   ```
+
+2. **Agent Modification**:
+   - Replace direct nixos-rebuild execution with: `systemctl start cm-rebuild`
+   - Stream output via: `journalctl -u cm-rebuild -f --no-pager`
+   - Monitor service status for completion detection
+
+3. **Benefits**:
+   - **Process Isolation**: Service runs independently, won't crash agent
+   - **Consistent Output**: Always same deterministic rebuild process
+   - **Proper Logging**: systemd journal handles all output management
+   - **Resource Management**: systemd manages cleanup and resource limits
+   - **Status Tracking**: Can query service status (running/failed/success)
+
+**Next Priority**: Implement systemd service approach for reliable rebuild operations.
+
 **Keyboard Controls Status:**
 - **Services Panel**: 
   - R (restart) ✅ Working