chore(vendor): import pi 0.85.1

Imported as a linear vendor commit so forge rebases do not replay the upstream root tree.

git-subtree-dir: third_party/pi

git-subtree-split: d981de1229ef899957bbe968bc8dcda02a21f477

third_party/pi/packages/ai/src/utils/headers.ts

@@ -0,0 +1,18 @@
+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()) {
+		result[key] = value;
+	}
+	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;
+}