feat(desktop): add recovery bridge methods to preload + types

- rendererReady (boot-completion ping)
- getRecoveryState / onRecoveryStateChanged (recovery.html subscribers)
- recoveryAction (button click dispatcher with enum action)

Type declarations kept ambient (no export) to preserve window.backspace
global augmentation — exporting from an ambient .d.ts converts it to a
module and breaks the Window interface extension.

packages/desktop/src/preload.ts

@@ -107,4 +107,23 @@ contextBridge.exposeInMainWorld('backspace', {
     return () => { ipcRenderer.removeListener('keybind-hook-error', handler); };
   },
   checkAccessibility: () => ipcRenderer.invoke('check-accessibility'),
+
+  // Recovery mode bridge (Task 11)
+  rendererReady: (): void => {
+    ipcRenderer.send('renderer-ready');
+  },
+
+  getRecoveryState: (): Promise<unknown> => {
+    return ipcRenderer.invoke('get-recovery-state');
+  },
+
+  onRecoveryStateChanged: (cb: (state: unknown) => void): (() => void) => {
+    const handler = (_e: Electron.IpcRendererEvent, state: unknown) => cb(state);
+    ipcRenderer.on('recovery-state-changed', handler);
+    return () => { ipcRenderer.removeListener('recovery-state-changed', handler); };
+  },
+
+  recoveryAction: (action: string): void => {
+    ipcRenderer.send('recovery-action', action);
+  },
 });