feat(android): music keeps playing with the screen off

While a track plays, the page asks the shell to stay awake
(playback:keep-alive): on Android the cast's foreground service and
visible WebView, with a notification; on desktop a power save blocker.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

2 files changed, 20 insertions, 2 deletions

diff --git a/packages/meshbay-client/src/main.js b/packages/meshbay-client/src/main.js
index 4c8707c..fa4f3ec 100644
--- a/packages/meshbay-client/src/main.js
+++ b/packages/meshbay-client/src/main.js
@@ -20,8 +20,8 @@
 
 'use strict';
 
-const { app, BrowserWindow, dialog, ipcMain, Menu, protocol, safeStorage,
-        shell, Tray } =
+const { app, BrowserWindow, dialog, ipcMain, Menu, powerSaveBlocker, protocol,
+        safeStorage, shell, Tray } =
   require('electron');
 const { execFile, spawn } = require('node:child_process');
 const crypto = require('node:crypto');
@@ -2304,6 +2304,19 @@ function registerBridge() {
     return true;
   });
 
+  // The screen may sleep while music plays; the machine may not, or the
+  // connection to the node goes with it.
+  let playbackBlocker = null;
+  handle('playback:keep-alive', async (_event, on) => {
+    if (on === true && playbackBlocker === null) {
+      playbackBlocker = powerSaveBlocker.start('prevent-app-suspension');
+    } else if (on !== true && playbackBlocker !== null) {
+      powerSaveBlocker.stop(playbackBlocker);
+      playbackBlocker = null;
+    }
+    return true;
+  });
+
   handle('cast:status', async () => ({
     active: castRelay.active,
     url: castRelay.url,
diff --git a/packages/meshbay-client/src/preload.js b/packages/meshbay-client/src/preload.js
index 43cf317..3af6c10 100644
--- a/packages/meshbay-client/src/preload.js
+++ b/packages/meshbay-client/src/preload.js
@@ -165,6 +165,11 @@ contextBridge.exposeInMainWorld('meshbay', {
     serviceMode: (action) => ipcRenderer.invoke('node:service-mode', action),
   },
 
+  // Music is playing: the machine must not idle-sleep under it.
+  playback: {
+    keepAlive: (on) => ipcRenderer.invoke('playback:keep-alive', on === true),
+  },
+
   // LAN cast relay. The main process runs a local HTTP server and the
   // renderer feeds it decrypted segments. A Chromecast or Smart TV on the
   // same Wi-Fi plays from the URL.