[fix](trx-frontend-http): pass rig_id to SSE endpoint on reconnect

After select_rig stopped mutating the global remote_active_rig_id for
session-aware clients, SSE reconnects would fall back to the old global
default instead of the newly selected rig. Now connect() passes
lastActiveRigId as a rig_id query param to /events, and the server
prefers it over the global default when present.

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/assets/web/app.js

@@ -3183,7 +3183,10 @@ function connect() {
     clearInterval(esHeartbeat);
   }
   pollFreshSnapshot();
-  es = new EventSource("/events");
+  const eventsUrl = lastActiveRigId
+    ? `/events?rig_id=${encodeURIComponent(lastActiveRigId)}`
+    : "/events";
+  es = new EventSource(eventsUrl);
   lastEventAt = Date.now();
   es.onopen = () => {
     setConnLostOverlay(false);