fix(extension): 扩展意图检测提前到 route_intent 之前

验收实测:『创建一个扩展用于统计 fastq 质量』被 route_intent 判
qa(生信词库不识别扩展创建语义),扩展意图判定在 bioflow 分支内
永远到不了。修复:扩展两层判定移到 gen() 开头,命中发
extension_* 帧后返回;不命中走原逻辑(漏判安全)。

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

bioflow_service/app/routers/bioflow.py

@@ -156,29 +156,10 @@ async def chat_stream(body: ChatStreamRequest) -> StreamingResponse:
     last_seq = body.last_seq if body.last_seq is not None else -1
 
     async def gen():
-        # 0. 生信流内流程咨询（has_bioflow_context + FLOW_QA_WORD）→ 知识库引用
-        intent = route_intent(
-            body.message,
-            has_attachments=body.has_attachments,
-            has_active_artifact=body.has_active_artifact,
-            has_bioflow_context=body.has_bioflow_context,
-        )
-        if intent == "bioflow_qa":
-            qa_payload = await flow_ask(FlowAskRequest(session_id=body.session_id, question=body.message))
-            yield _sse({"type": "message_done", "seq": -2, "data": {
-                "kind": "flow_qa",
-                "citations": qa_payload["answer"]["citations"],
-                "degraded": qa_payload["answer"]["degraded"],
-            }})
-            return
-        if intent != "bioflow":
-            yield _sse({"type": "message_done", "seq": -2, "data": {
-                "kind": "qa", "message": "已转交知识问答处理", "routed": intent,
-            }})
-            return
-
-        # 0.5. 扩展意图两层判定(契约 §5;先于阶段规划,漏判安全)。
-        # 命中 → 发 extension_* 引导帧后返回(不进入正常生信阶段规划)。
+        # 0. 扩展意图两层判定(契约 §5)——必须在 route_intent 之前:
+        # 「创建一个扩展用于…」这类消息会被生信词库判为 qa,永远到不了
+        # bioflow 分支;扩展判定先行,命中发 extension_* 帧后返回,
+        # 不命中走原 route_intent 逻辑(漏判安全,现网零影响)。
         from ..services.bioflow import extensions as ext_mod
         from ..services.bioflow.intent import detect_extension_intent
         try:
@@ -217,6 +198,27 @@ async def chat_stream(body: ChatStreamRequest) -> StreamingResponse:
         except Exception as exc:  # noqa: BLE001 - 扩展链路异常不回退生信主链
             logger.warning("chat_stream: extension intent check failed: %s", exc)
 
+        # 0. 生信流内流程咨询（has_bioflow_context + FLOW_QA_WORD）→ 知识库引用
+        intent = route_intent(
+            body.message,
+            has_attachments=body.has_attachments,
+            has_active_artifact=body.has_active_artifact,
+            has_bioflow_context=body.has_bioflow_context,
+        )
+        if intent == "bioflow_qa":
+            qa_payload = await flow_ask(FlowAskRequest(session_id=body.session_id, question=body.message))
+            yield _sse({"type": "message_done", "seq": -2, "data": {
+                "kind": "flow_qa",
+                "citations": qa_payload["answer"]["citations"],
+                "degraded": qa_payload["answer"]["degraded"],
+            }})
+            return
+        if intent != "bioflow":
+            yield _sse({"type": "message_done", "seq": -2, "data": {
+                "kind": "qa", "message": "已转交知识问答处理", "routed": intent,
+            }})
+            return
+
         # 1. 规划（候选路径；复用/LLM/降级）
         try:
             plan: PlanResult = await ctx.planner.plan(body.message)