fix: apply the non-productive stall budget to the ocr loop

Same failure path as the embedding loop: one timed-out attempt drains the
wall-clock window, and the next round without a runnable source declares
the scope dead in _on_no_runnable. All three governance loops now meter
stall the same way.

src/polygateway/ocr.py

@@ -35,7 +35,7 @@ from polygateway.errors import (
 )
 from polygateway.middleware.breaker import BreakerGate
 from polygateway.middleware.ratelimit import QuotaGate
-from polygateway.middleware.retry import _failure_reason, backoff_delay
+from polygateway.middleware.retry import StallClock, _failure_reason, backoff_delay
 from polygateway.middleware.telemetry import TelemetryEmitter
 from polygateway.ports import OutcomeAwareSelector
 from polygateway.sources import SourceCooldownMemo
@@ -204,13 +204,17 @@ class OcrClient:
             raise AllSourcesExhausted(scope=self._scope, reason="no_sources", retry_after_s=0.0)
         fails = 0
         reasons: dict[str, str] = {}
-        entered_at = self._now()
+        # 只计非生产性等待(issue #8): 真实尝试由重试预算治理,不重复烧 stall 预算
+        clock = StallClock(self._now)
         while True:
             picked, gate_rejections = await self._pick_runnable(reasons)
             if picked is None:
-                await self._on_no_runnable(gate_rejections, reasons, entered_at)
+                await self._on_no_runnable(gate_rejections, reasons, clock)
                 continue
-            outcome = await self._attempt(kind, image, *picked, reasons, session_id, parent_call_id)
+            async with clock.attempting():
+                outcome = await self._attempt(
+                    kind, image, *picked, reasons, session_id, parent_call_id
+                )
             if isinstance(outcome, _AttemptOutcome):
                 return outcome
             fails += 1
@@ -253,7 +257,7 @@ class OcrClient:
         return None, gate_rejections
 
     async def _on_no_runnable(
-        self, gate_rejections: int, reasons: dict[str, str], entered_at: float
+        self, gate_rejections: int, reasons: dict[str, str], clock: StallClock
     ) -> None:
         if gate_rejections == len(self._sources):
             names = tuple(s.name for s in self._sources)
@@ -270,7 +274,7 @@ class OcrClient:
                 per_source_reasons=reasons,
             )
         stall = self._bp.stall_window_s
-        if self._now() - entered_at > stall and await self._quota.progress_age_s() > stall:
+        if clock.stalled_s() > stall and await self._quota.progress_age_s() > stall:
             names = tuple(s.name for s in self._sources)
             raise AllSourcesExhausted(
                 scope=self._scope,