docs: correct how a wait-mode call actually dies on a dead source

Branch review caught the docs claiming something the code does not do.
CHANGELOG, README and the design's behaviour matrix all said a
force-opened source under circuit_open=wait waits out the full stall
window. It does not: the probe let through after each cooldown is a
real attempt, so it burns a max_attempts slot like any other, and a
401 source usually runs out of retry budget first -- reason is
retry_exhausted, not stalled. Which budget wins depends on
max_attempts against the cooldowns and the stall window.

The behaviour is right; only the prose was wrong. Charging the probe
to the retry budget is exactly the split issue #8 settled: the
question is who spends max_attempts, and a probe does send a real
request. A test now pins it so the claim cannot drift again.

Also drops the planned "woke up" log line. Each wait round already
logs on entry with its duration, and a still-blocked wake-up logs the
next round immediately, so a second line would only double the volume.

tests/unit/test_backpressure.py

@@ -16,6 +16,7 @@ from polygateway.errors import (
     CircuitOpenError,
     GatewayUnavailableError,
     GovernanceBackendError,
+    SourceDeadError,
     SourceNotConfiguredError,
     TransientError,
 )
@@ -742,6 +743,39 @@ class TestCircuitOpenPolicy:
         with pytest.raises(asyncio.CancelledError):
             await task
 
+    async def test_wait_does_not_exempt_probes_from_the_retry_budget(self):
+        """wait 档不豁免重试预算: 探针是**真实尝试**,失败照样烧 max_attempts。
+
+        故 force_open 的源(401/403/欠费一击即熔,不看任何阈值)在 wait 档下并
+        **不是**"等满 stall 窗口才死"——两个预算哪个先耗尽就以哪个的 reason
+        失败。这里 max_attempts=3 而冷却只累计 120s < stall_window=300s,故
+        先到的是重试预算。参数换成"冷却累计超过 stall 预算"则先到 stalled
+        (见 test_wait_still_dies_when_cooldown_outlasts_the_stall_budget)。
+
+        这与 issue #8 确立的划分一致: 划分依据是"谁消耗重试预算",探针发出了
+        真实请求,理应记在重试预算上而不是 stall 账上。
+        """
+        clock = FakeClock()
+        src = make_source()
+        sleep = BoundedSleep()
+
+        async def advance(_n):
+            clock.advance(sleep.delays[-1])
+
+        sleep._side_effect = advance
+        mw = _mw(
+            [src],
+            self._free_limiter(clock, src),
+            [SourceDeadError("401"), SourceDeadError("401"), SourceDeadError("401")],
+            clock=clock,
+            sleep=sleep,
+            circuit_open="wait",
+        )
+        with pytest.raises(AllSourcesExhausted) as ei:
+            await mw(_REQ)
+        assert ei.value.reason == "retry_exhausted"
+        assert clock.t - 1000.0 < _STALL  # 远未等满 stall 窗口
+
     async def test_half_open_rejection_does_not_blacklist_a_recovered_source(self):
         """issue #14 §1.3 回归: 探针成功后本进程立即可再选该源。