Bound sample wall clock; a request timeout does not stop a hang

One baseline sample sat on a single model request for 2h15m with an established
connection, 0.1% CPU and no file activity since the init solver wrote func.py. The
per-request timeout and max_retries did not bound it, and it blocked the rest of the run
behind it.

time_limit is the control that actually applies, per sample. Samples that finish take 8
to 15 minutes, so 30 is generous. An unbounded straggler costs more than the sample does.

Claude-Session: https://claude.ai/code/session_01Cq98H7sNoSJdL3W98f18bu

scripts/baseline.py

@@ -35,6 +35,12 @@ CONCURRENCY = int(os.environ.get("MBB_CONCURRENCY", "12"))
 # holding a slot for the length of the run, not to cut short slow thinking.
 REQUEST_TIMEOUT = int(os.environ.get("MBB_TIMEOUT", "900"))
 
+# Per-sample wall clock. One baseline sample hung on a single model request for
+# 2h15m with no file activity and never came back; the request timeout did not
+# bound it. Samples that finish take 8 to 15 minutes, so 30 is generous, and an
+# unbounded straggler blocking a whole run is worth more than the sample.
+SAMPLE_TIME_LIMIT = int(os.environ.get("MBB_SAMPLE_LIMIT", "1800"))
+
 
 def credits_used() -> float | None:
     """Total credits spent on the key so far, or None if the endpoint is unavailable."""
@@ -71,6 +77,7 @@ def run_split(split: str) -> dict:
         fail_on_error=False,
         timeout=REQUEST_TIMEOUT,
         max_retries=3,
+        time_limit=SAMPLE_TIME_LIMIT,
     )
     after = credits_used()
     log = logs[0]