feat: feed selector health and demote in-call failed sources

RetryMW keeps a per-call failure map (local, never instance state):
a source failing twice in one call yields to the next candidate.
Attempt outcomes feed OutcomeAwareSelector behind a swallow-and-warn
guard; ResultInvalid and provider-rejected paths record success with
count_attempt=False so the breaker window stays clean. Same accounting
applied in EmbeddingClient.

src/polygateway/ports.py

@@ -152,7 +152,9 @@ class ProviderGate(Protocol):
 
     async def try_enter(self, source_name: str, owner: str) -> GateDecision: ...
 
-    async def record_success(self, entry: GateDecision) -> GateUpdate: ...
+    async def record_success(
+        self, entry: GateDecision, *, count_attempt: bool = True
+    ) -> GateUpdate: ...
 
     async def record_failure(
         self, entry: GateDecision, reason: str, force_open: bool