fix(gateway): 熔断计入持续 4xx + 去 assert + Protocol/transient 去重

P1-2 非可重试错误(持续 401/403)也 record_failure，坏 key 可触发熔断。
P1-9 _complete_structured 的 assert 改显式 raise ValueError（-O 安全）。
P2 GatewayRun 抽到 orchestrator/_protocols.py 单点（去 4 处重复）；
  _is_transient 抽到 adapters/base.py is_transient_by_name（去 3 处重复）；
  Gemini Protocol 改 async def；gateway._retrying 去无用 async。

packages/llm_gateway/ww_llm_gateway/adapters/anthropic.py

@@ -16,7 +16,13 @@ from pydantic import BaseModel
 
 from ..errors import TransientProviderError
 from ..types import LlmRequest
-from .base import Capabilities, ProviderResult, ProviderUsage, StreamChunk
+from .base import (
+    Capabilities,
+    ProviderResult,
+    ProviderUsage,
+    StreamChunk,
+    is_transient_by_name,
+)
 
 if TYPE_CHECKING:
     from anthropic import AsyncAnthropic
@@ -44,11 +50,7 @@ class StructuredAnthropic(Protocol):
 
 
 def _is_transient(exc: Exception) -> bool:
-    name = type(exc).__name__
-    if name in _TRANSIENT_NAMES:
-        return True
-    status = getattr(exc, "status_code", None)
-    return isinstance(status, int) and (status == 429 or status >= 500)
+    return is_transient_by_name(exc, _TRANSIENT_NAMES)
 
 
 def _system_blocks(req: LlmRequest) -> list[dict[str, Any]]:
@@ -144,7 +146,8 @@ class AnthropicAdapter:
         return ProviderResult(text=_text_from(resp), usage=usage)
 
     async def _complete_structured(self, req: LlmRequest, model: str) -> ProviderResult:
-        assert req.output_schema is not None
+        if req.output_schema is None:
+            raise ValueError("_complete_structured called without output_schema")
         kwargs: dict[str, Any] = {
             "model": model,
             "max_tokens": req.max_tokens or _DEFAULT_MAX_TOKENS,

packages/llm_gateway/ww_llm_gateway/adapters/base.py

@@ -12,6 +12,34 @@ from pydantic import BaseModel, ConfigDict
 
 from ..types import LlmRequest
 
+# 瞬时（可退避重试）的 HTTP 状态码判定：429 限流 或 5xx 服务端错误。
+_RATE_LIMITED_STATUS = 429
+_SERVER_ERROR_MIN_STATUS = 500
+
+
+def _is_transient_status(status: object) -> bool:
+    return isinstance(status, int) and (
+        status == _RATE_LIMITED_STATUS or status >= _SERVER_ERROR_MIN_STATUS
+    )
+
+
+def is_transient_by_name(
+    exc: Exception, names: frozenset[str], *, extra_codes: bool = False
+) -> bool:
+    """统一的瞬时错误判定（DRY：三个适配器共用）。
+
+    ① 异常类名命中 `names`（按名匹配，避免硬依赖各厂商 SDK 异常类型）；或
+    ② `status_code` 属性是 429/5xx；或
+    ③ `extra_codes=True` 时额外检查 `code` 属性是否为 429/5xx（Gemini 用 `exc.code`）。
+    """
+    if type(exc).__name__ in names:
+        return True
+    if _is_transient_status(getattr(exc, "status_code", None)):
+        return True
+    if extra_codes and _is_transient_status(getattr(exc, "code", None)):
+        return True
+    return False
+
 
 class Capabilities(BaseModel):
     structured_output: bool = False

packages/llm_gateway/ww_llm_gateway/adapters/gemini.py

@@ -14,7 +14,13 @@ from typing import Any, Protocol
 
 from ..errors import TransientProviderError
 from ..types import LlmRequest
-from .base import Capabilities, ProviderResult, ProviderUsage, StreamChunk
+from .base import (
+    Capabilities,
+    ProviderResult,
+    ProviderUsage,
+    StreamChunk,
+    is_transient_by_name,
+)
 
 _TRANSIENT_NAMES = frozenset(
     {
@@ -31,7 +37,7 @@ _TRANSIENT_NAMES = frozenset(
 class GeminiModels(Protocol):
     async def generate_content(self, **kwargs: Any) -> Any: ...
 
-    def generate_content_stream(self, **kwargs: Any) -> Any: ...
+    async def generate_content_stream(self, **kwargs: Any) -> Any: ...
 
 
 class GeminiAio(Protocol):
@@ -45,11 +51,8 @@ class GeminiClient(Protocol):
 
 
 def _is_transient(exc: Exception) -> bool:
-    name = type(exc).__name__
-    if name in _TRANSIENT_NAMES:
-        return True
-    status = getattr(exc, "code", None) or getattr(exc, "status_code", None)
-    return isinstance(status, int) and (status == 429 or status >= 500)
+    # Gemini SDK 部分错误用 `exc.code` 携带状态码 → extra_codes=True 一并检查。
+    return is_transient_by_name(exc, _TRANSIENT_NAMES, extra_codes=True)
 
 
 def _contents(req: LlmRequest) -> str:

packages/llm_gateway/ww_llm_gateway/adapters/openai_compat.py

@@ -15,7 +15,13 @@ from pydantic import BaseModel
 
 from ..errors import TransientProviderError
 from ..types import LlmRequest
-from .base import Capabilities, ProviderResult, ProviderUsage, StreamChunk
+from .base import (
+    Capabilities,
+    ProviderResult,
+    ProviderUsage,
+    StreamChunk,
+    is_transient_by_name,
+)
 
 # OpenAI 兼容 SDK 的瞬时错误类名（按名匹配，覆盖 DeepSeek/Kimi/Qwen/GLM 等共用 SDK）。
 _TRANSIENT_NAMES = frozenset(
@@ -30,11 +36,7 @@ _TRANSIENT_NAMES = frozenset(
 
 
 def _is_transient(exc: Exception) -> bool:
-    name = type(exc).__name__
-    if name in _TRANSIENT_NAMES:
-        return True
-    status = getattr(exc, "status_code", None)
-    return isinstance(status, int) and (status == 429 or status >= 500)
+    return is_transient_by_name(exc, _TRANSIENT_NAMES)
 
 
 class StructuredClient(Protocol):
@@ -126,7 +128,8 @@ class OpenAICompatAdapter:
         return ProviderResult(text=text, usage=_usage_from(resp.usage))
 
     async def _complete_structured(self, req: LlmRequest, model: str) -> ProviderResult:
-        assert req.output_schema is not None
+        if req.output_schema is None:
+            raise ValueError("_complete_structured called without output_schema")
         parsed, raw = await self._structured().create_with_completion(
             messages=_messages(req),
             response_model=req.output_schema,