refactor: unify model picker behavior

Share model picker UI across chat, agents, and multi-run
Prefer live provider limits with metadata fallback

packages/ui/src/lib/modelMetadata.ts

@@ -0,0 +1,35 @@
+import type { ModelMetadata } from '@/types';
+
+type LiveProviderModel = Record<string, unknown> & { id?: string; name?: string };
+
+const getNumericLimit = (limit: unknown, key: 'context' | 'output') => {
+  if (!limit || typeof limit !== 'object') return undefined;
+  const value = (limit as Record<string, unknown>)[key];
+  return typeof value === 'number' && Number.isFinite(value) ? value : undefined;
+};
+
+export const mergeModelMetadataWithLiveModel = (
+  providerId: string,
+  model: LiveProviderModel,
+  metadata?: ModelMetadata,
+): ModelMetadata | undefined => {
+  const liveContextLimit = getNumericLimit(model.limit, 'context');
+  const liveOutputLimit = getNumericLimit(model.limit, 'output');
+  const contextLimit = liveContextLimit ?? metadata?.limit?.context;
+  const outputLimit = liveOutputLimit ?? metadata?.limit?.output;
+
+  if (contextLimit === undefined && outputLimit === undefined) return metadata;
+
+  return {
+    ...(metadata ?? {
+      id: typeof model.id === 'string' ? model.id : '',
+      providerId,
+      name: typeof model.name === 'string' ? model.name : undefined,
+    }),
+    limit: {
+      ...metadata?.limit,
+      ...(contextLimit !== undefined ? { context: contextLimit } : {}),
+      ...(outputLimit !== undefined ? { output: outputLimit } : {}),
+    },
+  };
+};