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/tests/fakes_resilience.py

@@ -108,6 +108,22 @@ def transient(msg: str = "boom") -> TransientProviderError:
     return TransientProviderError(msg)
 
 
+class AuthError(Exception):
+    """模拟持续性鉴权失败（坏 key / 账号被禁）：带 `status_code`，**非**瞬时不可重试。
+
+    适配器对 401/403 不翻译为 `TransientProviderError`，原样上抛；网关须对其计入熔断
+    （P1-2）而非每次白打同一坏 provider。
+    """
+
+    def __init__(self, msg: str = "unauthorized", *, status_code: int = 401) -> None:
+        super().__init__(msg)
+        self.status_code = status_code
+
+
+def auth_error(status_code: int = 401) -> AuthError:
+    return AuthError(status_code=status_code)
+
+
 def chain(*routes: tuple[str, str]) -> list[Route]:
     return [Route(provider=p, model=m) for p, m in routes]
 

packages/llm_gateway/tests/test_fallback_chain.py

@@ -8,7 +8,15 @@
 from __future__ import annotations
 
 import pytest
-from fakes_resilience import FakeLedger, ScriptedAdapter, chain, chain_resolver, transient
+from fakes_resilience import (
+    AuthError,
+    FakeLedger,
+    ScriptedAdapter,
+    auth_error,
+    chain,
+    chain_resolver,
+    transient,
+)
 from ww_llm_gateway.gateway import CircuitBreaker, Gateway
 from ww_llm_gateway.types import LlmRequest
 from ww_shared import AppError, ErrorCode
@@ -154,6 +162,39 @@ def test_circuit_breaker_reopens_after_cooldown() -> None:
     assert cb.is_open("deepseek") is False
 
 
+async def test_persistent_auth_error_counts_toward_breaker(req: LlmRequest) -> None:
+    """P1-2：持续性 401（坏 key）虽不可重试，但应计入熔断——连续 N 次后熔断打开。
+
+    每次 `run` 命中 401 立即上抛（不重试、不回退），但 raise 前 `record_failure`；
+    达到阈值后熔断打开，后续请求直接跳过该 provider → 链耗尽抛 LLM_UNAVAILABLE。
+    """
+    threshold = 3
+    primary = ScriptedAdapter("deepseek", failures=[auth_error() for _ in range(threshold + 2)])
+    cb = CircuitBreaker(threshold=threshold, reset_seconds=60.0)
+    gw = Gateway(
+        {"deepseek": primary},
+        FakeLedger(),
+        chain_resolver=chain_resolver(chain(("deepseek", "deepseek-chat"))),
+        breaker=cb,
+    )
+
+    # 前 threshold 次：401 原样上抛（不可重试），但每次计一次熔断失败。
+    for _ in range(threshold):
+        assert cb.is_open("deepseek") is False
+        with pytest.raises(AuthError):
+            await gw.run(req)
+
+    # 第 threshold 次失败后熔断打开。
+    assert cb.is_open("deepseek") is True
+
+    # 后续请求：provider 被熔断跳过 → 不再调 complete，链耗尽 → LLM_UNAVAILABLE。
+    calls_before = primary.complete_calls
+    with pytest.raises(AppError) as exc:
+        await gw.run(req)
+    assert exc.value.code == ErrorCode.LLM_UNAVAILABLE
+    assert primary.complete_calls == calls_before  # 熔断后未再触达坏 provider
+
+
 async def test_open_circuit_skips_provider(req: LlmRequest) -> None:
     # 熔断已打开的主 provider 被直接跳过，连 complete 都不调，直接走回退。
     primary = ScriptedAdapter("deepseek", text="不该被调")