fix(smolmachines): stop VM before pack commit, with confirm prompt

smolvm pack create --from-vm requires the VM to be stopped. Add
machine_is_running() to smolvm.py (via machine ls --json state field),
and add the same confirm-stop flow to SmolmachinesFreezer that was
originally designed for macos-container: if running, prompt the user,
stop the VM, then pack. Already-stopped VMs are packed directly.

bot_bottle/backend/smolmachines/smolvm.py

@@ -25,6 +25,7 @@ smolvm binary."""
 
 from __future__ import annotations
 
+import json
 import shutil
 import subprocess
 import time
@@ -153,6 +154,21 @@ def machine_create(
     _smolvm(*args)
 
 
+def machine_is_running(name: str) -> bool:
+    """Return True if the named VM is in the 'running' state."""
+    result = _smolvm("machine", "ls", "--json", check=False)
+    if result.returncode != 0:
+        return False
+    try:
+        machines = json.loads(result.stdout or "[]")
+    except ValueError:
+        return False
+    return any(
+        isinstance(m, dict) and m.get("name") == name and m.get("state") == "running"
+        for m in machines
+    )
+
+
 def machine_start(name: str) -> None:
     """`smolvm machine start --name NAME`."""
     _smolvm("machine", "start", "--name", name)