feat(cast): music on the TV, the music bar as its remote

A cast button in Music's toolbar and in the music bar. With a television
chosen, each decrypted track goes to the relay with its cover — found as the
album card finds it — and plays there as music with its title, artist and
album; the bar's play, pause, seek, previous and next drive the receiver, its
clock is the receiver's, and the end of a track there moves the queue on.
A film or a photo taking the television pauses the bar; stopping the cast
carries the track on locally.

Photos and tracks now share one path: a whole file sent to the relay in
pieces (binary frames on Android, written to disk there), served at /file
with byte ranges and its cover at /cover, and loaded as what the relay says
it is. cast:image is gone; cast:chromecast:seek is new.

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

1 files changed, 16 insertions, 14 deletions

diff --git a/packages/meshbay-client/src/main.js b/packages/meshbay-client/src/main.js
index 1c371f5..a2a7a86 100644
--- a/packages/meshbay-client/src/main.js
+++ b/packages/meshbay-client/src/main.js
@@ -2333,29 +2333,31 @@ function registerBridge() {
 
   handle('cast:devices', async () => castChromecast.devices());
 
-  // One photo at a time, scaled and re-encoded by the page.
-  handle('cast:image', async (_e, img) => {
-    return castRelay.showImage({ bytes: Buffer.from(img.bytes), type: img.type });
-  });
+  // A whole file for the receiver — a photo, a music track — in three steps,
+  // so that a large one never crosses in a single message.
+  handle('cast:file:begin', async (_e, f) => castRelay.beginFile(f || {}));
+  handle('cast:file:write', async (_e, data) => castRelay.writeFile(Buffer.from(data)));
+  handle('cast:file:end', async () => castRelay.endFile());
 
-  // The relay's photo is loaded as a picture, anything else as the stream;
-  // the page does not get to say which.
+  // The relay's file is loaded as what the relay says it is, anything else as
+  // the stream; the page does not get to say which.
   const loadOf = (mediaUrl, subtitle) => (
-    mediaUrl && mediaUrl === castRelay.imageUrl
-      ? { subtitle: null, contentType: castRelay.imageType }
-      : { subtitle: subtitle === undefined ? castRelay.subtitle : subtitle,
-          contentType: 'video/mp4' });
+    mediaUrl && mediaUrl === castRelay.fileUrl
+      ? { subtitle: null, file: { contentType: castRelay.fileType, meta: castRelay.fileMeta } }
+      : { subtitle: subtitle === undefined ? castRelay.subtitle : subtitle, file: null });
 
-  handle('cast:chromecast:connect', async (_e, { deviceId, mediaUrl, subtitle }) => {
+  handle('cast:chromecast:connect', async (_e, { deviceId, mediaUrl, subtitle, startAt }) => {
     const l = loadOf(mediaUrl, subtitle);
-    return castChromecast.connect(deviceId, mediaUrl, l.subtitle, l.contentType);
+    return castChromecast.connect(deviceId, mediaUrl, l.subtitle, l.file, l.file ? startAt : 0);
   });
 
-  handle('cast:chromecast:reload', async (_e, { mediaUrl, subtitle }) => {
+  handle('cast:chromecast:reload', async (_e, { mediaUrl, subtitle, startAt }) => {
     const l = loadOf(mediaUrl, subtitle);
-    return castChromecast.reload(mediaUrl, l.subtitle, l.contentType);
+    return castChromecast.reload(mediaUrl, l.subtitle, l.file, l.file ? startAt : 0);
   });
 
+  handle('cast:chromecast:seek', async (_e, seconds) => castChromecast.seek(seconds));
+
   // The player becomes a remote while casting: these drive the receiver.
   handle('cast:chromecast:pause', async () => castChromecast.pause());
   handle('cast:chromecast:play', async () => castChromecast.play());