style: reformat three files the current ruff would rewrite

Not related to the schema work. These three fail ruff format --check on
main as well -- the pinned ruff is newer than whatever last formatted
them -- and a red make check makes the per-task quality gate useless for
everything that follows.

tests/unit/test_backpressure.py

@@ -321,9 +321,7 @@ class TestStallBudget:
         async def advance(_n):
             clock.advance(_STALL)
 
-        mw = _mw(
-            [src], limiter, [], clock=clock, sleep=BoundedSleep(advance), transport=transport
-        )
+        mw = _mw([src], limiter, [], clock=clock, sleep=BoundedSleep(advance), transport=transport)
         with pytest.raises(AllSourcesExhausted) as ei:
             await mw(_REQ)
         assert ei.value.reason == "stalled"  # 不是 retry_exhausted: 429 确实没烧重试预算
@@ -541,9 +539,7 @@ class TestUnknownSourceIsAssemblyDefect:
         """
         src = make_source("s1")
         # 限流后端的源名单与治理循环拿到的源对不上 = 装配缺陷
-        limiter = InMemoryLimiter(
-            scope="llm", sources={"other": src}, global_limits=_NO_GLOBAL
-        )
+        limiter = InMemoryLimiter(scope="llm", sources={"other": src}, global_limits=_NO_GLOBAL)
         gate = QuotaGate(limiter, scope="llm")
         with pytest.raises(SourceNotConfiguredError) as ei:
             await getattr(gate, method)(src)