feat(ai): complete models runtime migration

packages/ai/src/utils/headers.ts

@@ -1,3 +1,5 @@
+import type { ProviderHeaders } from "../types.ts";
+
 export function headersToRecord(headers: Headers): Record<string, string> {
 	const result: Record<string, string> = {};
 	for (const [key, value] of headers.entries()) {
@@ -5,3 +7,12 @@ export function headersToRecord(headers: Headers): Record<string, string> {
 	}
 	return result;
 }
+
+export function providerHeadersToRecord(headers: ProviderHeaders | undefined): Record<string, string> | undefined {
+	if (!headers) return undefined;
+	const result: Record<string, string> = {};
+	for (const [key, value] of Object.entries(headers)) {
+		if (value !== null) result[key] = value;
+	}
+	return Object.keys(result).length > 0 ? result : undefined;
+}