feat(tier2): C1 trace 中间件接 with_studio(开 Studio 即旁路推 OTLP span)

C1 此前建了 observability.with_studio + studio_sink(OTLP→Studio),但没 wire 进真正跑的
Tier2TraceMiddleware(它在 worker/middleware.py、C1 没动)。本提交把中间件新建 adapter 的路径从
TraceAdapter(...) 换成 with_studio(...):drop-in——TIER2_STUDIO_URL/infra_config[studio] 取不到时
studio sink 自动 no-op,行为与原 TraceAdapter 完全一致(CLI/服务两线不开 Studio 即无感);取到地址则
每步在原 sink 外旁路推一份 OTLP span 给 AgentScope Studio(observe-only,best-effort,不阻塞主链)。
存 _studio_sink 句柄供收口 flush。配合 mini-desktop 起 Studio(创始人:now)即得真跑可视化。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tier2/gen-worker/worker/middleware.py

@@ -64,14 +64,14 @@ except Exception:  # pragma: no cover —— 直跑兜底:worker 包未就位时
 #   make_phase_marker / PHASE_* 是 U3 给三道新钩子产「相位段」typed event 用的(走 adapter 同一条 ingest 路)。
 try:
     from observability.trace import (  # type: ignore
-        TraceAdapter, make_phase_marker, PHASE_REASONING, PHASE_ACTING, PHASE_MODEL_CALL)
+        TraceAdapter, with_studio, make_phase_marker, PHASE_REASONING, PHASE_ACTING, PHASE_MODEL_CALL)
 except Exception:  # pragma: no cover —— 直跑/路径未就位兜底:把 gen-worker/ 加进 sys.path 再取
     import sys
     from pathlib import Path
 
     sys.path.insert(0, str(Path(__file__).resolve().parents[1]))
     from observability.trace import (  # type: ignore
-        TraceAdapter, make_phase_marker, PHASE_REASONING, PHASE_ACTING, PHASE_MODEL_CALL)
+        TraceAdapter, with_studio, make_phase_marker, PHASE_REASONING, PHASE_ACTING, PHASE_MODEL_CALL)
 
 # 成本折算(¥ 累进硬熔断用):compute 折单条 usage → ¥(纯函数,显式传参);活价取不到时回落次数闸。
 #   newapi_pricing.fetch_pricing_params 一步取齐 new-api 计费三件套(失败 best-effort 返回 None)。
@@ -521,8 +521,13 @@ class Tier2TraceMiddleware(MiddlewareBase):
         """
         self.trace_id = trace_id
         # 复用传入 adapter 或新建;adapter 是 trace 的产出件(H1/H2),本 middleware 只负责把事件喂进去。
-        self.adapter = adapter or TraceAdapter(
+        #   新建走 with_studio(C1 接线):若 TIER2_STUDIO_URL / infra_config[studio] 可解析,则每步在原 sink
+        #   之外旁路推一份 OTLP span 给 AgentScope Studio(observe-only);取不到地址 → studio sink 自动 no-op,
+        #   行为 == 原 TraceAdapter(sink=...),零影响(故 CLI/服务两条线都白拿 Studio 可观测、不开即无感)。
+        self.adapter = adapter or with_studio(
             trace_id=trace_id, sink=sink, keep_in_memory=keep_in_memory)
+        # studio sink 句柄(收口 flush 残留 span 用;with_studio 把它挂在 adapter._studio_sink,无则 None)。
+        self._studio_sink = getattr(self.adapter, "_studio_sink", None)
         # 兜底层告警计数(adapter 自身抛异常的极端情况;正常应为 0,因 adapter 内部已 best-effort)。
         self._middleware_dropped = 0