Add desktop runtime API and SDK support

docs/inspector.mdx

@@ -34,6 +34,7 @@ console.log(url);
 - Event JSON inspector
 - Prompt testing
 - Request/response debugging
+- Desktop panel for status, remediation, start/stop, and screenshot refresh
 - Process management (create, stop, kill, delete, view logs)
 - Interactive PTY terminal for tty processes
 - One-shot command execution
@@ -49,3 +50,16 @@ console.log(url);
 The Inspector includes an embedded Ghostty-based terminal for interactive tty
 processes. The UI uses the SDK's high-level `connectProcessTerminal(...)`
 wrapper via the shared `@sandbox-agent/react` `ProcessTerminal` component.
+
+## Desktop panel
+
+The `Desktop` panel shows the current desktop runtime state, missing dependencies,
+the suggested install command, last error details, process/log paths, and the
+latest captured screenshot.
+
+Use it to:
+
+- Check whether desktop dependencies are installed
+- Start or stop the managed desktop runtime
+- Refresh desktop status
+- Capture a fresh screenshot on demand