fix: require authoritative container snapshot before reconciling

A failed container list or a partial per-container inspect were
previously indistinguishable from a legitimately empty/partial live
set, so reconciliation could silently unregister healthy bottles.

- enumerate_active() now raises EnumerationError instead of returning []
  when `container list` fails
- Add inspect_container_network_ip() to util, which returns None on
  inspect failure (vs "" for "no DHCP address yet"), so live_source_ips
  can tell the two apart
- live_source_ips() raises EnumerationError on either failure mode;
  register_agent() catches it and skips reconciliation, same as
  OrchestratorClientError
- Update tests: rename test_empty_when_the_cli_fails to
  test_raises_when_the_cli_fails, update patching to the new function,
  add coverage for list failure, per-container inspect failure, and the
  launch-not-blocked path

tests/unit/test_macos_container_cleanup.py

@@ -66,8 +66,10 @@ class TestMacosContainerEnumerate(unittest.TestCase):
         agents = self._enumerate("bot-bottle-mac-infra\nbot-bottle-dev-abc\n")
         self.assertEqual(["dev-abc"], [a.slug for a in agents])
 
-    def test_empty_when_the_cli_fails(self):
-        self.assertEqual([], self._enumerate("", returncode=1))
+    def test_raises_when_the_cli_fails(self):
+        from bot_bottle.backend.macos_container.enumerate import EnumerationError
+        with self.assertRaises(EnumerationError):
+            self._enumerate("", returncode=1)
 
 
 if __name__ == "__main__":