fix: guard against undefined currentModelOption in effort selector

When a model stored in localStorage doesn't exist in the current
provider's model list (e.g. switching from Bailian's qwen3.5-plus to
Kimi which doesn't have it), currentModelOption could be undefined,
crashing with "Cannot read properties of undefined (reading
'supportsEffort')".

- MessageInput.tsx: add optional chaining on currentModelMeta access
- useProviderModels.ts: fall back to DEFAULT_MODEL_OPTIONS when
  provider's models array is empty

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 7418

src/components/chat/MessageInput.tsx

@@ -311,9 +311,9 @@ export function MessageInput({
     [popover, slashCommands, cliToolsFetch, badge, cliBadge, inputValue, removeBadge, removeCliBadge]
   );
 
-  // Effort selector state
-  const currentModelMeta = currentModelOption as typeof currentModelOption & { supportsEffort?: boolean; supportedEffortLevels?: string[] };
-  const showEffortSelector = currentModelMeta.supportsEffort === true;
+  // Effort selector state — guard against undefined when model not found in current provider's list
+  const currentModelMeta = currentModelOption as (typeof currentModelOption & { supportsEffort?: boolean; supportedEffortLevels?: string[] }) | undefined;
+  const showEffortSelector = currentModelMeta?.supportsEffort === true;
   const [localEffort, setLocalEffort] = useState<string>('high');
   const selectedEffort = effortProp ?? localEffort;
   const setSelectedEffort = useCallback((v: string) => {
@@ -432,7 +432,7 @@ export function MessageInput({
                   <EffortSelectorDropdown
                     selectedEffort={selectedEffort}
                     onEffortChange={setSelectedEffort}
-                    supportedEffortLevels={currentModelMeta.supportedEffortLevels}
+                    supportedEffortLevels={currentModelMeta?.supportedEffortLevels}
                   />
                 )}
 

src/hooks/useProviderModels.ts

@@ -60,7 +60,9 @@ export function useProviderModels(
   // Derive flat model list for current provider
   const currentProviderIdValue = providerId || defaultProviderId || (providerGroups[0]?.provider_id ?? '');
   const currentGroup = providerGroups.find(g => g.provider_id === currentProviderIdValue) || providerGroups[0];
-  const modelOptions = currentGroup?.models || DEFAULT_MODEL_OPTIONS;
+  const modelOptions = (currentGroup?.models && currentGroup.models.length > 0)
+    ? currentGroup.models
+    : DEFAULT_MODEL_OPTIONS;
 
   const currentModelValue = modelName || 'sonnet';
   const currentModelOption = useMemo(