feat(v2): Web 界面（对话/协作过程/人工检验/指标）+ worker 优雅降级

gateway/api.py

@@ -107,6 +107,9 @@ class HealthResponse(BaseModel):
 # ---- FastAPI 应用 ----
 try:
     from fastapi import FastAPI, HTTPException
+    from fastapi.responses import HTMLResponse
+
+    _INDEX_PATH = Path(__file__).resolve().parent / "static" / "index.html"
 
     app = FastAPI(
         title="端云协同 LLM 协作系统",
@@ -118,6 +121,13 @@ try:
     async def health():
         return get_router().health()
 
+    @app.get("/", response_class=HTMLResponse, tags=["ui"])
+    async def index():
+        """端云协同 Web 界面（单文件前端，无需构建）。"""
+        if _INDEX_PATH.exists():
+            return HTMLResponse(_INDEX_PATH.read_text(encoding="utf-8"))
+        return HTMLResponse("<h1>Web 界面未生成</h1><p>缺少 gateway/static/index.html</p>")
+
     # ---------------- v2：/chat ----------------
     @app.post("/chat", tags=["chat"])
     async def chat(req: QueryRequest):