fix: keep provider discovery on mockable lazy runtime paths

src/agents/provider-model-normalization.runtime.ts

@@ -0,0 +1,39 @@
+import { createRequire } from "node:module";
+
+type ProviderRuntimeModule = Pick<
+  typeof import("../plugins/provider-runtime.js"),
+  "normalizeProviderModelIdWithPlugin"
+>;
+
+const require = createRequire(import.meta.url);
+const PROVIDER_RUNTIME_CANDIDATES = [
+  "../plugins/provider-runtime.js",
+  "../plugins/provider-runtime.ts",
+] as const;
+
+let providerRuntimeModule: ProviderRuntimeModule | undefined;
+
+function loadProviderRuntime(): ProviderRuntimeModule | null {
+  if (providerRuntimeModule) {
+    return providerRuntimeModule;
+  }
+  for (const candidate of PROVIDER_RUNTIME_CANDIDATES) {
+    try {
+      providerRuntimeModule = require(candidate) as ProviderRuntimeModule;
+      return providerRuntimeModule;
+    } catch {
+      // Try source/runtime candidates in order.
+    }
+  }
+  return null;
+}
+
+export function normalizeProviderModelIdWithRuntime(params: {
+  provider: string;
+  context: {
+    provider: string;
+    modelId: string;
+  };
+}): string | undefined {
+  return loadProviderRuntime()?.normalizeProviderModelIdWithPlugin(params);
+}