fix: load OpenRouter models on kanban board without visiting settings

Problem:
- OpenRouter dynamic models only appeared after visiting settings page
- PhaseModelSelector (used in Add/Edit Feature dialogs) only fetched Codex models
- dynamicOpencodeModels remained empty until OpencodeSettingsTab mounted

Solution:
- Add fetchOpencodeModels() action to app-store mirroring fetchCodexModels pattern
- Add state tracking: opencodeModelsLoading, opencodeModelsError, timestamps
- Call fetchOpencodeModels() in PhaseModelSelector useEffect on mount
- Use same caching strategy: 5min success cache, 30sec failure cooldown

Files changed:
- apps/ui/src/store/app-store.ts
  - Add OpenCode model loading state properties
  - Add fetchOpencodeModels action with error handling & caching
- apps/ui/src/components/views/settings-view/model-defaults/phase-model-selector.tsx
  - Add opencodeModelsLoading, fetchOpencodeModels to store hook
  - Add useEffect to fetch OpenCode models on mount

Result:
- OpenRouter models now appear in Add/Edit Feature dialogs immediately
- No need to visit settings page first
- Consistent with Codex model loading behavior

apps/ui/src/components/views/settings-view/model-defaults/phase-model-selector.tsx

@@ -166,6 +166,8 @@ export function PhaseModelSelector({
     codexModelsLoading,
     fetchCodexModels,
     dynamicOpencodeModels,
+    opencodeModelsLoading,
+    fetchOpencodeModels,
   } = useAppStore();
 
   // Detect mobile devices to use inline expansion instead of nested popovers
@@ -185,6 +187,15 @@ export function PhaseModelSelector({
     }
   }, [codexModels.length, codexModelsLoading, fetchCodexModels]);
 
+  // Fetch OpenCode models on mount
+  useEffect(() => {
+    if (dynamicOpencodeModels.length === 0 && !opencodeModelsLoading) {
+      fetchOpencodeModels().catch(() => {
+        // Silently fail - user will see only static OpenCode models
+      });
+    }
+  }, [dynamicOpencodeModels.length, opencodeModelsLoading, fetchOpencodeModels]);
+
   // Close expanded group when trigger scrolls out of view
   useEffect(() => {
     const triggerElement = expandedTriggerRef.current;