feat(extension-health): lengthen cache TTL and honor per-check minimum

Raise default extension health cache to 10 minutes with a 1-minute floor
and a shorter TTL for unknown status. Mirror the TTL rules in the Go
backend and stop force-refreshing health checks from the download
service picker on every open.

go_backend/extension_health.go

@@ -15,8 +15,9 @@ import (
 const (
 	extensionHealthDefaultTimeout = 4 * time.Second
 	extensionHealthMaxBodyBytes   = 64 * 1024
-	extensionHealthDefaultCache   = 60 * time.Second
-	extensionHealthUnknownCache   = 20 * time.Second
+	extensionHealthDefaultCache   = 10 * time.Minute
+	extensionHealthMinCache       = 60 * time.Second
+	extensionHealthUnknownCache   = 2 * time.Minute
 )
 
 type ExtensionHealthResult struct {
@@ -166,6 +167,9 @@ func extensionHealthCacheTTL(checks []ExtensionHealthCheck) time.Duration {
 			continue
 		}
 		checkTTL := time.Duration(check.CacheTTLSeconds) * time.Second
+		if checkTTL < extensionHealthMinCache {
+			checkTTL = extensionHealthMinCache
+		}
 		if checkTTL < ttl {
 			ttl = checkTTL
 		}

lib/providers/extension_provider.dart

@@ -808,7 +808,9 @@ class ExtensionInstallBatchResult {
 }
 
 class ExtensionNotifier extends Notifier<ExtensionState> {
-  static const _extensionHealthCacheTtl = Duration(seconds: 60);
+  static const _extensionHealthDefaultCacheTtl = Duration(minutes: 10);
+  static const _extensionHealthMinimumCacheTtl = Duration(minutes: 1);
+  static const _extensionHealthUnknownCacheTtl = Duration(minutes: 2);
   AppLifecycleListener? _appLifecycleListener;
   bool _cleanupInFlight = false;
   Completer<void>? _initializationCompleter;
@@ -970,6 +972,34 @@ class ExtensionNotifier extends Notifier<ExtensionState> {
     _scheduleExtensionHealthRefresh(state.extensions, force: force);
   }
 
+  Duration _extensionHealthCacheTtlFor(Extension extension) {
+    var ttl = _extensionHealthDefaultCacheTtl;
+    for (final check in extension.serviceHealth) {
+      final seconds = check.cacheTtlSeconds;
+      if (seconds == null || seconds <= 0) continue;
+
+      var checkTtl = Duration(seconds: seconds);
+      if (checkTtl < _extensionHealthMinimumCacheTtl) {
+        checkTtl = _extensionHealthMinimumCacheTtl;
+      }
+      if (checkTtl < ttl) {
+        ttl = checkTtl;
+      }
+    }
+    return ttl;
+  }
+
+  Duration _extensionHealthCacheTtlForStatus(
+    Extension extension,
+    String status,
+  ) {
+    final ttl = _extensionHealthCacheTtlFor(extension);
+    if (status == 'unknown' && ttl > _extensionHealthUnknownCacheTtl) {
+      return _extensionHealthUnknownCacheTtl;
+    }
+    return ttl;
+  }
+
   Future<ExtensionHealthStatus?> checkExtensionHealth(
     String extensionId, {
     bool force = false,
@@ -1007,7 +1037,7 @@ class ExtensionNotifier extends Notifier<ExtensionState> {
             state.healthStatuses,
           )..[extensionId] = status;
           _healthExpiresAt[extensionId] = DateTime.now().add(
-            _extensionHealthCacheTtl,
+            _extensionHealthCacheTtlForStatus(ext, status.status),
           );
           state = state.copyWith(healthStatuses: updated);
         }
@@ -1025,7 +1055,7 @@ class ExtensionNotifier extends Notifier<ExtensionState> {
             state.healthStatuses,
           )..[extensionId] = status;
           _healthExpiresAt[extensionId] = DateTime.now().add(
-            const Duration(seconds: 20),
+            _extensionHealthUnknownCacheTtl,
           );
           state = state.copyWith(healthStatuses: updated);
         }

lib/widgets/download_service_picker.dart

@@ -75,9 +75,7 @@ class _DownloadServicePickerState extends ConsumerState<DownloadServicePicker> {
     super.initState();
     WidgetsBinding.instance.addPostFrameCallback((_) {
       if (!mounted) return;
-      ref
-          .read(extensionProvider.notifier)
-          .refreshEnabledExtensionHealth(force: true);
+      ref.read(extensionProvider.notifier).refreshEnabledExtensionHealth();
     });
     final downloadExtensions = _downloadExtensions();
     final recommended = widget.recommendedService;
@@ -109,9 +107,7 @@ class _DownloadServicePickerState extends ConsumerState<DownloadServicePicker> {
     setState(() => _selectedService = extension.id);
     if (extension.hasServiceHealth) {
       unawaited(
-        ref
-            .read(extensionProvider.notifier)
-            .checkExtensionHealth(extension.id, force: true),
+        ref.read(extensionProvider.notifier).checkExtensionHealth(extension.id),
       );
     }
   }