feat(costs): add billing, quota, and budget control plane

packages/adapter-utils/src/billing.ts

@@ -0,0 +1,20 @@
+function readEnv(env: NodeJS.ProcessEnv, key: string): string | null {
+  const value = env[key];
+  return typeof value === "string" && value.trim().length > 0 ? value.trim() : null;
+}
+
+export function inferOpenAiCompatibleBiller(
+  env: NodeJS.ProcessEnv,
+  fallback: string | null = "openai",
+): string | null {
+  const explicitOpenRouterKey = readEnv(env, "OPENROUTER_API_KEY");
+  if (explicitOpenRouterKey) return "openrouter";
+
+  const baseUrl =
+    readEnv(env, "OPENAI_BASE_URL") ??
+    readEnv(env, "OPENAI_API_BASE") ??
+    readEnv(env, "OPENAI_API_BASE_URL");
+  if (baseUrl && /openrouter\.ai/i.test(baseUrl)) return "openrouter";
+
+  return fallback;
+}