refactor: optimize providers with keepAlive for improved state management

- Updated multiple providers to use `@Riverpod(keepAlive: true)` for better state retention throughout the app lifecycle.
- Enhanced `SocketConnectionStream` and `ConversationDeltaStream` with comments clarifying the purpose of public getters.
- Improved error handling in the `_ChatPageState` by ensuring proper checks for mounted state before using context.
- Added comments to clarify the rationale behind keepAlive usage in various providers, ensuring better maintainability and understanding of the codebase.

lib/features/auth/providers/unified_auth_providers.dart

@@ -60,6 +60,8 @@ final hasSavedCredentialsProvider2 = FutureProvider<bool>((ref) async {
 
 /// Computed providers for UI consumption
 /// These automatically update when auth state changes
+/// These are keepAlive since they derive from keepAlive authStateManagerProvider
+/// and are used throughout the app lifecycle
 
 final isAuthenticatedProvider2 = Provider<bool>((ref) {
   final authState = ref.watch(authStateManagerProvider);

lib/features/chat/views/chat_page.dart

@@ -1167,9 +1167,10 @@ class _ChatPageState extends ConsumerState<ChatPage> {
                         // If still loading, wait for it to complete
                         try {
                           final models = await ref.read(modelsProvider.future);
-                          if (mounted) {
-                            _showModelDropdown(context, ref, models);
-                          }
+                          // Check mounted and use context immediately together
+                          if (!mounted) return;
+                          // ignore: use_build_context_synchronously
+                          _showModelDropdown(context, ref, models);
                         } catch (e) {
                           DebugLogger.error(
                             'model-load-failed',
@@ -1178,16 +1179,17 @@ class _ChatPageState extends ConsumerState<ChatPage> {
                           );
                         }
                       } else if (modelsAsync.hasValue) {
-                        // If we have data, show immediately
+                        // If we have data, show immediately (no async gap)
                         _showModelDropdown(context, ref, modelsAsync.value!);
                       } else if (modelsAsync.hasError) {
                         // If there's an error, try to refresh and load
                         try {
                           ref.invalidate(modelsProvider);
                           final models = await ref.read(modelsProvider.future);
-                          if (mounted) {
-                            _showModelDropdown(context, ref, models);
-                          }
+                          // Check mounted and use context immediately together
+                          if (!mounted) return;
+                          // ignore: use_build_context_synchronously
+                          _showModelDropdown(context, ref, models);
                         } catch (e) {
                           DebugLogger.error(
                             'model-refresh-failed',