fix(model-resolver): use connected providers cache when model cache is empty (#1227)

- Remove resolved.model from userModel in tools.ts (was bypassing fallback chain)
- Use connected providers cache in model-resolver when availableModels is empty
- Allows proper provider selection (e.g., github-copilot instead of google)

src/tools/delegate-task/tools.ts

@@ -537,7 +537,7 @@ To continue this session: session_id="${args.session_id}"`
            }
           } else {
           const resolution = resolveModelWithFallback({
-              userModel: userCategories?.[args.category]?.model ?? resolved.model ?? sisyphusJuniorModel,
+              userModel: userCategories?.[args.category]?.model ?? sisyphusJuniorModel,
               fallbackChain: requirement.fallbackChain,
               availableModels,
               systemDefaultModel,