Keep the per-call I/O deadline over endpoint setup as well as the reply

The per-call deadline moved inside _request, which no longer bounded
endpoint setup and its retries: an io() against an absent peer waited the
client's full retry budget. The outer deadline is back around the call;
the inner one still keeps the query to a single attempt.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Author: Jepson2k

parol6/client/async_client.py

@@ -902,7 +902,13 @@ async def io(self, *, timeout: float | None = None) -> list[int] | None:
             isinstance(timeout, bool) or not math.isfinite(timeout) or timeout <= 0
         ):
             raise ValueError("I/O timeout must be positive and finite")
-        resp = await self._request(IOCmd(), timeout=timeout)
+        # The outer deadline also bounds endpoint setup and its retries on an
+        # absent peer; the inner one keeps the query to a single attempt.
+        try:
+            async with asyncio.timeout(timeout):
+                resp = await self._request(IOCmd(), timeout=timeout)
+        except TimeoutError:
+            return None
         return resp.io if isinstance(resp, IOResultStruct) else None
 
     async def joint_speeds(self) -> list[float] | None: