style: pass explicit check= to every subprocess.run call

Silences pylint W1510 / ruff PLW1510 across the codebase. The choice
at each site reflects existing intent:

- check=True where the caller implicitly trusts success (docker ps /
  network ls returning stdout, docker build, exec chown/chmod inside
  provisioners).
- check=False where the caller inspects .returncode (race-retry on
  docker run, pipelock sidecar lifecycle, network plumbing, exec_claude
  propagating the session's exit code, best-effort cleanup paths).

No behavior change; check= defaults to False so the False sites are
semantically identical.

tests/integration/test_pipelock_sidecar_smoke.py

@@ -46,6 +46,7 @@ class TestPipelockSidecarSmoke(unittest.TestCase):
             ["docker", "pull", CURL_IMAGE],
             stdout=subprocess.DEVNULL,
             stderr=subprocess.DEVNULL,
+            check=False,
         )
         if result.returncode != 0:
             raise unittest.SkipTest(f"could not pull {CURL_IMAGE}")
@@ -104,6 +105,7 @@ class TestPipelockSidecarSmoke(unittest.TestCase):
             capture_output=True,
             text=True,
             timeout=60,
+            check=False,
         )
         self.assertEqual(
             0, probe.returncode,