DEVX-155: fix: trust /var/run/docker.sock with free=0 when no inner dockerd exists

The host's rootless Docker socket is mounted as /var/run/docker.sock
inside CI containers. Its data root is on the host filesystem (not
accessible from inside the container), so _get_docker_free_bytes
returns 0. Previously the code didn't trust this and started a local
dockerd on /dev/shm (too small). Now checks pgrep for dockerd processes
— if none found inside the container, the socket is the host's Docker
and should be trusted.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

src/devx/molecule/start_docker.py

@@ -210,6 +210,22 @@ def start_docker_daemon(timeout: int = DEFAULT_TIMEOUT) -> bool:
         if free_bytes == 0 and sock == HOST_DOCKER_SOCK:
             click.echo("Host rootless Docker root dir not accessible from container, using it")
             return True
+        # If free_bytes is 0 and there are no dockerd processes inside the
+        # container, the socket is the host's Docker (mounted from outside).
+        # The data root is on the host filesystem and has plenty of space.
+        if free_bytes == 0 and sock == DOCKER_SOCK:
+            has_inner_dockerd = False
+            with contextlib.suppress(Exception):
+                pgrep_result = subprocess.run(  # nosec B603 B607
+                    ["pgrep", "-f", "dockerd"],
+                    capture_output=True,
+                    text=True,
+                    timeout=5,
+                )
+                has_inner_dockerd = pgrep_result.returncode == 0
+            if not has_inner_dockerd:
+                click.echo("No inner dockerd found, socket is host Docker (data root on host), using it")
+                return True
         click.echo(f"  Insufficient space ({free_gb:.1f} GB), trying next...")
 
     # No socket with sufficient space found.