fix(studio): connect to the active channel, not hard-coded :50051

Studio defaulted its endpoint to the local channel's port (:50051), but
a curl|sh user is on the production channel (:50071) — so the sidebar
probed a different daemon than the Diagnose page reported, showing
'connected' next to 'production daemon stopped'. On first run Studio now
reads ~/.chain/current-channel (+ run/<ch>.endpoint) and follows the
active channel; an explicit Settings endpoint still wins and persists,
auto-discovery does not (re-follows the channel each launch). The
connection caption now names the channel ('Connected · production') so
it can never look contradictory again.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/main.dart

@@ -763,8 +763,11 @@ class _SidebarState extends State<_Sidebar>
                   Builder(
                     builder: (context) {
                       final l = AppLocalizations.of(context)!;
+                      final ch = HubService.instance.connectedChannelName;
                       final caption = widget.connected == true
-                          ? l.connectionConnected
+                          ? (ch != null
+                                ? '${l.connectionConnected} · $ch'
+                                : l.connectionConnected)
                           : widget.connected == false
                           ? l.connectionTapToStart
                           : l.connectionConnecting;
@@ -1127,8 +1130,12 @@ class _ConnectionLabel extends StatelessWidget {
     final captionColor = connected == false
         ? theme.colorScheme.error
         : theme.colorScheme.onSurface;
+    // Name the channel the connection is on (production / local / …) so
+    // "connected" can never look like it contradicts the Diagnose page,
+    // which reports the *active* channel's daemon.
+    final ch = HubService.instance.connectedChannelName;
     final caption = connected == true
-        ? l.connectionConnected
+        ? (ch != null ? '${l.connectionConnected} · $ch' : l.connectionConnected)
         : connected == false
         ? l.connectionTapToStart
         : l.connectionConnecting;