perf: trim live-status batch IPC payload + skip empty broadcasts

The live-status batch poller (60s cadence, every streamer in the
watch list) was sending two things on every tick:
- `changes` — the diff vs. the previous tick, used by the renderer
- `snapshot` — the full Map<login, boolean> serialized as a record

Renderer destructures only `changes` (renderer-streamers.ts line 20).
The snapshot field was wire-noise. For a typical 30-50 streamer
watch list, that snapshot is ~1.5KB of JSON every minute, never
read on the other side. Dropped from the broadcast payload.

Initial-state sync still works: the renderer's
initLiveStatusSubscription calls window.api.getLiveStatusSnapshot()
once at boot to pre-fill its map. The broadcast is only for diffs.

Also added a short-circuit on the main side: if changes.length === 0
(every streamer's live status matched the cached value this tick),
don't broadcast at all. The renderer would just iterate an empty
array and trigger a no-op render; saves the wakeup entirely.

Type signature updates ride through preload.ts +
renderer-globals.d.ts so the API contract stays accurate.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/main.ts

@@ -3770,10 +3770,13 @@ async function runLiveStatusBatchPoll(): Promise<void> {
             }
         }
 
-        if (mainWindow) {
-            const snapshot: Record<string, boolean> = {};
-            for (const [k, v] of liveStatusByLogin.entries()) snapshot[k] = v;
-            mainWindow.webContents.send('live-status-batch-update', { changes, snapshot });
+        if (mainWindow && changes.length > 0) {
+            // Renderer only consumes `changes` — initial state comes via
+            // the get-live-status-snapshot IPC at boot. Don't ship the
+            // full map on every tick (was ~1.5KB JSON per 60s with zero
+            // consumer-side use). Also skip the broadcast entirely when
+            // nothing actually changed.
+            mainWindow.webContents.send('live-status-batch-update', { changes });
         }
     } catch (e) {
         appendDebugLog('live-status-poll-failed', String(e));

src/preload.ts

@@ -94,7 +94,7 @@ contextBridge.exposeInMainWorld('api', {
     getStreamerProfile: (login: string, forceRefresh?: boolean) => ipcRenderer.invoke('get-streamer-profile', login, forceRefresh),
     getVodStoryboard: (vodId: string) => ipcRenderer.invoke('get-vod-storyboard', vodId),
     getLiveStatusSnapshot: () => ipcRenderer.invoke('get-live-status-snapshot'),
-    onLiveStatusBatchUpdate: (callback: (info: { changes: Array<{ login: string; isLive: boolean }>; snapshot: Record<string, boolean> }) => void) => {
+    onLiveStatusBatchUpdate: (callback: (info: { changes: Array<{ login: string; isLive: boolean }> }) => void) => {
         ipcRenderer.on('live-status-batch-update', (_, info) => callback(info));
     },
     searchArchive: (filter: Record<string, unknown>) => ipcRenderer.invoke('search-archive', filter),

src/renderer-globals.d.ts

@@ -347,7 +347,7 @@ interface ApiBridge {
     getStreamerProfile(login: string, forceRefresh?: boolean): Promise<StreamerProfile | null>;
     getVodStoryboard(vodId: string): Promise<VodStoryboard | null>;
     getLiveStatusSnapshot(): Promise<Record<string, boolean>>;
-    onLiveStatusBatchUpdate(callback: (info: { changes: Array<{ login: string; isLive: boolean }>; snapshot: Record<string, boolean> }) => void): void;
+    onLiveStatusBatchUpdate(callback: (info: { changes: Array<{ login: string; isLive: boolean }> }) => void): void;
     searchArchive(filter: {
         query?: string;
         type?: 'all' | 'live' | 'vod' | 'chat' | 'events';