Send videos to Gemini at 3 fps and allow larger WebSocket payloads

Map video_url parts to inline data for Google and attach
videoMetadata.fps = 3 to every video part (media resolution stays at
the default). Raise the WebSocket maxPayloadLength from Bun's 16 MB
default to 100 MB so threads with several base64 videos still fit.

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

index.js

@@ -48,6 +48,8 @@ Bun.serve({
   },
 
   websocket: {
+    // Videos ride along as base64 in every request; Bun's 16 MB default fits only a handful
+    maxPayloadLength: 100 * 1024 * 1024,
     open(ws) {
       const { uid } = ws.data
       addSocket(uid, ws)