feat(API-11): Route API calls through AgilitonAPI gateway

Add gateway-first pattern: when AGILITON_API_KEY is set, route all
external API calls through the gateway with X-API-Key auth. Falls back
to direct API access when gateway is unavailable.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

node_modules/@modelcontextprotocol/sdk/dist/cjs/shared/stdio.d.ts

@@ -0,0 +1,13 @@
+import { JSONRPCMessage } from '../types.js';
+/**
+ * Buffers a continuous stdio stream into discrete JSON-RPC messages.
+ */
+export declare class ReadBuffer {
+    private _buffer?;
+    append(chunk: Buffer): void;
+    readMessage(): JSONRPCMessage | null;
+    clear(): void;
+}
+export declare function deserializeMessage(line: string): JSONRPCMessage;
+export declare function serializeMessage(message: JSONRPCMessage): string;
+//# sourceMappingURL=stdio.d.ts.map