DEVX-30: fix: use DOCKER_HOST env var in is_docker_ready + scan all rootless sockets

.taskid

@@ -1 +1 @@
-DEVX-29
+DEVX-30

src/devx/molecule/molecule_ci_guard.py

@@ -321,6 +321,17 @@ def cli(pairs: tuple[str, ...], junit_output: str | None, roles_root: Path | Non
 
             click.echo(_("PASSED: {pair}", pair=pair))
 
+            # Prune Docker data between scenarios to prevent disk exhaustion
+            # in Docker-in-Docker molecule containers (each scenario pulls
+            # hundreds of MB of images that accumulate across pairs).
+            with contextlib.suppress(subprocess.SubprocessError, OSError):
+                subprocess.run(  # nosec B603, B607
+                    ["docker", "system", "prune", "-af", "--volumes"],
+                    check=False,
+                    capture_output=True,
+                    timeout=60,
+                )
+
         click.echo(_("All molecule tests passed."))
         if junit_output:
             write_junit_report(junit_output, testcases, current_index)

tests/unit/test_molecule_ci_guard.py

@@ -162,17 +162,26 @@ class TestCli:
 
         with (
             patch("devx.molecule.molecule_ci_guard.subprocess.Popen") as mock_popen,
+            patch("devx.molecule.molecule_ci_guard.subprocess.run") as mock_run,
             patch("time.sleep"),
         ):
             proc = MagicMock()
             proc.poll.return_value = 0
             proc.returncode = 0
             mock_popen.return_value = proc
+            mock_run.return_value = MagicMock(returncode=0)
 
             runner = CliRunner()
             result = runner.invoke(cli, ["default|ubuntu-2204|img:latest|"])
             assert result.exit_code == 0
             assert "All molecule tests passed" in result.output
+            # Verify Docker prune was called between scenarios
+            mock_run.assert_called_once_with(
+                ["docker", "system", "prune", "-af", "--volumes"],
+                check=False,
+                capture_output=True,
+                timeout=60,
+            )
 
     def test_invalid_pair_format_raises(self) -> None:
         """Pair with fewer than 2 parts should raise."""
@@ -324,6 +333,7 @@ class TestCli:
             ),
             patch("devx.molecule.molecule_ci_guard.POLL_INTERVAL", 0.01),
             patch("devx.molecule.molecule_ci_guard.subprocess.Popen") as mock_popen,
+            patch("devx.molecule.molecule_ci_guard.subprocess.run") as mock_run,
             patch("devx.molecule.molecule_ci_guard.get_running_jobs") as mock_get_jobs,
             patch("time.sleep", side_effect=lambda x: real_sleep(0.05)),
         ):
@@ -332,6 +342,7 @@ class TestCli:
             proc.poll.return_value = 0
             proc.returncode = 0
             mock_popen.return_value = proc
+            mock_run.return_value = MagicMock(returncode=0)
 
             runner = CliRunner()
             result = runner.invoke(cli, ["default|ubuntu-2204|img:latest|"])
@@ -536,12 +547,14 @@ class TestCliMultiRole:
 
         with (
             patch("devx.molecule.molecule_ci_guard.subprocess.Popen") as mock_popen,
+            patch("devx.molecule.molecule_ci_guard.subprocess.run") as mock_run,
             patch("time.sleep"),
         ):
             proc = MagicMock()
             proc.poll.return_value = 0
             proc.returncode = 0
             mock_popen.return_value = proc
+            mock_run.return_value = MagicMock(returncode=0)
 
             runner = CliRunner()
             result = runner.invoke(
@@ -560,12 +573,14 @@ class TestCliMultiRole:
 
         with (
             patch("devx.molecule.molecule_ci_guard.subprocess.Popen") as mock_popen,
+            patch("devx.molecule.molecule_ci_guard.subprocess.run") as mock_run,
             patch("time.sleep"),
         ):
             proc = MagicMock()
             proc.poll.return_value = 0
             proc.returncode = 0
             mock_popen.return_value = proc
+            mock_run.return_value = MagicMock(returncode=0)
 
             runner = CliRunner()
             result = runner.invoke(