Fix lint: add noqa for runtime FastAPI imports in standalone SDK

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: timmeck

nexus/sdk_standalone.py

@@ -38,7 +38,7 @@ async def handle_text_gen(query: str, params: dict) -> dict:
 from typing import Any
 
 import httpx
-from fastapi import FastAPI, Request
+from fastapi import FastAPI, Request  # noqa: TC002 (runtime: route registration)
 from pydantic import BaseModel, Field
 
 log = logging.getLogger("nexus.sdk")