feat: LAN Wi-Fi casting to Chromecast via local HTTP relay

Re-serve decrypted fMP4 video over HTTP on the LAN so a Chromecast can
play the stream. The relay runs in the Electron main process — same trust
boundary as downloads and MSE playback.

- cast-relay.js: HTTP server with BoxAccumulator (reassembles WebRTC
  chunks into moof+mdat pairs), ring buffer, backpressure, finish() for
  clean end-of-stream, fixed port range 19550-19553
- cast-chromecast.js: mDNS discovery (bonjour-service) + CASTV2 protocol
  (castv2-client), connect/reload/disconnect lifecycle
- Seek-aware: relay restarts on every seek, Chromecast reloads new URL;
  generation counter prevents stale async errors from killing active
  restarts; landingPlayheadRef suppresses programmatic seeking events
- Device picker in video top bar with scan, device selection, copy-URL
  fallback, and cast status indicator
- IPC bridge (main/preload/platform) for start/push/stop/finish/status/
  discover/chromecastConnect/chromecastReload/chromecastDisconnect
- Phase 3 design doc for DLNA/Smart TV in docs/cast-smart-tv.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/transport.js b/packages/meshbay-hub/src/meshbay_hub/static/transport.js
index 17886f4..2cdf15d 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/transport.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/transport.js
@@ -742,12 +742,14 @@ class MeshBayTransport {
     // `start` is a seek: the node retires whatever this session was streaming
     // and spawns ffmpeg again from there. Omitted or zero is the film's
     // beginning, which is what an 0.1 node understands.
+    console.log('[stream] sending stream_req start:', start, 'credits:', credits);
     this._send({ type: 'stream_req', v: '0.1', file_id: fileId, credits, start });
   }
 
   /** Room for `n` more segments. */
   grantStreamCredit(n = 1) {
     if (!this._connected) return;
+    console.log('[stream] grant credit:', n);
     this._send({ type: 'stream_more', v: '0.1', n });
   }
 
@@ -1200,6 +1202,7 @@ class MeshBayTransport {
       return;
     }
     if (msg.type === 'stream_init') {
+      console.log('[stream] recv stream_init, start:', msg.start, 'codec:', msg.codec, 'handler:', !!this._onStreamInit);
       if (this._onStreamInit) this._onStreamInit(msg);
       return;
     }
@@ -1208,6 +1211,7 @@ class MeshBayTransport {
       return;
     }
     if (msg.type === 'stream_end') {
+      console.log('[stream] recv stream_end');
       if (this._onStreamEnd) this._onStreamEnd(msg);
       return;
     }