[fix](trx-frontend-http): stop per-rig audio fallback to global broadcast

When ?rig_id= is specified on /audio, don't fall back to the global broadcast (which carries whichever rig is connected). Return 404 for rigs without an active audio connection instead of silently delivering the wrong rig's audio. Also create per-rig audio channels for all known rigs eagerly so connected rigs are instantly subscribable.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-client/trx-frontend/trx-frontend-http/src/audio.rs

@@ -519,15 +519,20 @@ pub async fn audio_ws(
         }
     } else if let Some(ref rig_id) = query.rig_id {
         // Per-rig audio: subscribe to the specific rig's broadcast.
-        match context.rig_audio_subscribe(rig_id) {
-            Some(rx) => rx,
-            None => {
-                // Rig not yet connected; fall back to global.
-                let Some(rx) = context.audio_rx.as_ref() else {
-                    return Ok(HttpResponse::NotFound().body("audio not enabled"));
-                };
-                rx.subscribe()
+        // Do NOT fall back to global — that would silently deliver the wrong
+        // rig's audio. Wait briefly for the per-rig channel to appear (it is
+        // lazily created by the audio relay sync task every 500ms).
+        let deadline = Instant::now() + Duration::from_secs(3);
+        loop {
+            if let Some(rx) = context.rig_audio_subscribe(rig_id) {
+                break rx;
             }
+            if Instant::now() >= deadline {
+                return Ok(
+                    HttpResponse::NotFound().body(format!("audio not available for rig {rig_id}"))
+                );
+            }
+            tokio::time::sleep(Duration::from_millis(100)).await;
         }
     } else {
         let Some(rx) = context.audio_rx.as_ref() else {