fix(security): harden privileged renderer boundaries

Reject renderer-owned queue internals before persistence and bind privileged handlers to trusted renderer events. Extend cutter session capabilities without weakening owner, purpose, path identity, or expiry checks. Migrate release harness contracts to opaque capabilities and add an invisible Node gate.

src/preload.ts

@@ -112,7 +112,7 @@ contextBridge.exposeInMainWorld('api', {
 
     // Queue
     getQueue: () => ipcRenderer.invoke('get-queue'),
-    addToQueue: (item: Omit<QueueItem, 'id' | 'status' | 'progress'>) => ipcRenderer.invoke('add-to-queue', item),
+    addToQueue: (item: Pick<QueueItem, 'url' | 'title' | 'date' | 'streamer' | 'duration_str' | 'customClip'>) => ipcRenderer.invoke('add-to-queue', item),
     startLiveRecording: (streamerName: string) => ipcRenderer.invoke('start-live-recording', streamerName),
     removeFromQueue: (id: string) => ipcRenderer.invoke('remove-from-queue', id),
     reorderQueue: (orderIds: string[]) => ipcRenderer.invoke('reorder-queue', orderIds),