fix(#80): only URL/port gate a broker enable; firmware owns the rest

On-hardware feedback: JWT owner defaults to the device pubkey and IATA override
is optional by definition, so gating a save on them is wrong -- they have
under-the-hood firmware defaults.

BrokerConfig.enableError now checks only the structural fields with no default:
URL present, port in range. The JWT field checks are gone; the firmware enforces
JWT completeness with its defaults, and a genuinely-bad enable surfaces the
firmware's reason via the failure messaging added earlier. The editor's pre-save
check and the list's quick Enable both follow.

Tests updated to the new contract (a JWT broker with blank owner/audience now
enables; a structurally-complete quick Enable confirms). Full suite green.

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

lib/models/observer_config.dart

@@ -150,10 +150,8 @@ class BrokerConfig {
   String? get enableError {
     if (url.isEmpty) return 'URL is required';
     if (port < 1 || port > 65535) return 'Port must be between 1 and 65535';
-    if (authType == BrokerAuthType.jwt &&
-        (jwtAudience.isEmpty || jwtOwner.isEmpty)) {
-      return 'JWT auth needs an audience and an owner';
-    }
+    // JWT owner (device pubkey), IATA override, etc. are firmware-defaulted, so
+    // the client does NOT gate them — the firmware enforces with its defaults.
     return null;
   }
 

lib/screens/settings/broker_editor_screen.dart

@@ -113,14 +113,12 @@ class _BrokerEditorScreenState extends State<BrokerEditorScreen> {
       _changedFields().isNotEmpty || _enabled != _baseline.enabled;
 
   /// Pre-enable validation, shared with the list's quick Enable via
-  /// [BrokerConfig.enableError]. Builds a tentative config from the form.
+  /// [BrokerConfig.enableError]. Only structural fields (URL, port) gate a save
+  /// — the firmware enforces the rest via its own defaults.
   String? _validate() => BrokerConfig(
     slot: _baseline.slot,
     url: _url.text.trim(),
     port: int.tryParse(_port.text.trim()) ?? -1,
-    authType: _authType,
-    jwtAudience: _jwtAudience.text.trim(),
-    jwtOwner: _jwtOwner.text.trim(),
   ).enableError;
 
   void _snack(String msg, {bool isError = false}) {

test/screens/broker_editor_screen_test.dart

@@ -203,7 +203,9 @@ void main() {
     await _drainSnack(tester);
   });
 
-  testWidgets('enabling with incomplete JWT is blocked', (tester) async {
+  testWidgets('a JWT broker with blank owner/audience still enables', (
+    tester,
+  ) async {
     final fake = _FakeSvc();
     await _open(
       tester,
@@ -212,7 +214,8 @@ void main() {
         slot: 2,
         url: 'h',
         port: 1883,
-        authType: BrokerAuthType.jwt, // disabled, blank audience/owner
+        authType:
+            BrokerAuthType.jwt, // blank owner/audience -> firmware default
       ),
     );
 
@@ -221,8 +224,14 @@ void main() {
     await tester.tap(find.byTooltip('Save'));
     await tester.pumpAndSettle();
 
-    expect(fake.saveCalls, isEmpty);
-    expect(find.textContaining('needs an audience'), findsOneWidget);
+    expect(
+      fake.saveCalls,
+      hasLength(1),
+      reason:
+          'the client no longer gates JWT fields — the firmware enforces them '
+          'with its defaults (owner -> device pubkey)',
+    );
+    expect(fake.saveCalls.single.enable, isTrue);
     await _drainSnack(tester);
   });
 }

test/screens/mqtt_brokers_screen_test.dart

@@ -102,12 +102,8 @@ void main() {
     expect(fake.clearCalls, contains(2));
   });
 
-  testWidgets('quick Enable refuses an incomplete broker with a reason', (
-    tester,
-  ) async {
-    final fake = _FakeSvc(const [
-      BrokerConfig(slot: 2, url: 'a', port: 1883, authType: BrokerAuthType.jwt),
-    ]);
+  testWidgets('a successful quick Enable confirms', (tester) async {
+    final fake = _FakeSvc(const [BrokerConfig(slot: 2, url: 'a', port: 1883)]);
     await _pump(tester, fake);
 
     await tester.longPress(find.text('[2] a'));
@@ -115,12 +111,8 @@ void main() {
     await tester.tap(find.text('Enable'));
     await tester.pumpAndSettle();
 
-    expect(
-      fake.setCalls,
-      isEmpty,
-      reason: 'an incomplete broker must not be enabled',
-    );
-    expect(find.textContaining("Can't enable"), findsOneWidget);
+    expect(fake.setCalls, contains('2.enabled=1'));
+    expect(find.textContaining('enabled'), findsOneWidget);
     await tester.pump(const Duration(seconds: 5));
   });