music sidecar: raise Bun.serve idleTimeout (blocking reindex outran 10s default)

The one-time v1→v2 full rebuild (and long range/SSE reads) take far longer than
Bun.serve's default 10s request idle-timeout, which dropped the triggering
request mid-flight ("request timed out after 10 seconds"). Set idleTimeout: 255
(Bun's max). A build that still outruns it completes in the background regardless
— a closed socket doesn't cancel the in-flight build promise.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/servers/sidecar/music/index.ts

@@ -74,6 +74,10 @@ const port = getFreePort();
 const server = Bun.serve({
   port,
   hostname: '127.0.0.1',
+  // A blocking /reindex (esp. the one-time full rebuild) and long range/SSE reads far outlast Bun's
+  // default 10s request idle-timeout, which would drop them mid-flight. 255s is Bun's max; a build that
+  // still outruns it completes in the background anyway (the promise isn't cancelled by a closed socket).
+  idleTimeout: 255,
   async fetch(req) {
     const url = new URL(req.url);
     const json = (data: unknown, init?: ResponseInit) =>