Fix: relay WebSocket messages as text frames (browsers got Blobs they could not parse)

Root cause of 'track does not start': the server re-broadcast incoming frames as
binary (Buffer), so the browser output page received Blobs, JSON.parse failed,
and every command (playTrack, etc.) was silently dropped — only the text-encoded
lastEffect sync got through. Broadcast as text now; net.js also handles Blob
defensively. Also: no-store for app assets + kiosk --disk-cache-size=1 so
redeploys always take effect; /api/clients debug endpoint; /api/peaks duration.

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

public/js/output.js

@@ -341,6 +341,9 @@ djv.onControl(async (m) => {
         djv.report({ type: 'playState', playing: true });
       } catch (e) { djv.report({ type: 'error', message: e.message }); }
       break;
+    case 'diag':
+      djv.report({ type: 'diag', stage: 'poll', ctx: audio.ctx.state, mode: audio.mode });
+      break;
     case 'playVideoTrack':
       try {
         audio.setTrim(m.start || 0, m.end || 0);