fix(tests): watchdog exits with code 2 so run_tests_batched.py sees the timeout

The conftest watchdog (e1c8730f) used os._exit(0) after the 30s sleep. run_tests_batched.py calls subprocess.run(check=True) and only prints 'Batch N failed.' when the subprocess exits non-zero. Exit 0 hid the failure: pytest got killed mid-test, the FAILURES section never printed, and the runner silently moved to the next batch. The 'Total batches with failures: 1' summary at the end was therefore undercounting.

Fix: os._exit(0) -> os._exit(2). Code 2 is the standard 'interrupted by signal/timeout' code; pytest also uses it for Ctrl-C. The batched runner now correctly reports a non-zero exit as a failure.

Test updated (docstring) to document the new contract. 3/3 test_conftest_watchdog.py still pass.

tests/conftest.py

@@ -77,7 +77,7 @@ if not _warmup_app_controller.wait_for_warmup(timeout=60.0):
 def _watchdog_exit() -> None:
  import time
  time.sleep(30.0)
- os._exit(0)
+ os._exit(2)
 import threading
 threading.Thread(target=_watchdog_exit, daemon=True, name="conftest-hang-watchdog").start()
 

tests/test_conftest_watchdog.py

@@ -9,12 +9,19 @@ observed:
      hanging on HTTP call to the hook server or on process.wait() for
      the sloppy.py subprocess.
 
-The conftest installs a daemon-thread watchdog (os._exit(0) after a
-timeout) to bound the hang. This test verifies the watchdog is
-actually registered after the conftest loads. It does NOT spawn a
-subprocess (which would itself be bound by the watchdog and create a
-recursive timeout), it just inspects threading.enumerate() at the
-time the test runs.
+The conftest installs a daemon-thread watchdog (os._exit(2) after a
+30s timeout) to bound the hang. The non-zero exit code is critical:
+run_tests_batched.py uses subprocess.run(check=True) and only
+prints "Batch N failed." if pytest exits non-zero. Exit code 0 would
+silently report a successful batch even when the watchdog killed
+pytest mid-test (the FAILURES section never gets printed). Exit
+code 2 is the standard "interrupted by signal/timeout" code that
+preserves the failure signal to the runner.
+
+This test verifies the watchdog is actually registered after the
+conftest loads. It does NOT spawn a subprocess (which would itself
+be bound by the watchdog and create a recursive timeout), it just
+inspects threading.enumerate() at the time the test runs.
 
 If the watchdog is removed or the timeout grows, this test fails
 and the run_tests_batched.py hang returns.