fix(macos-container): commit via exec-tar instead of stop→export

Apple Container removes containers when they stop, making the
stop-then-export flow impossible regardless of the --rm flag.

Replace `container export` (requires stopped container) with
`container exec --user root <name> tar --create ... --file=- --directory=/ .`
streamed to a temp file, then build the committed image from that archive
as before. The bottle stays running after commit, which is better UX.

Drop the stop-confirm prompt from MacosContainerFreezer since we no longer
need to stop the container at all.

bot_bottle/backend/macos_container/freezer.py

@@ -1,37 +1,26 @@
 """MacosContainerFreezer — snapshot a macOS container bottle.
 
-Apple's `container export` requires the container to be stopped first.
-When the container is running the freezer prompts the user to confirm
-the stop before proceeding."""
+Apple Container removes containers when they stop, making stop-then-export
+impossible. Instead, commit_container execs into the running container and
+streams the root filesystem via tar. The bottle continues running after commit.
+"""
 
 from __future__ import annotations
 
-import sys
-
 from .. import ActiveAgent
-from ..freeze import CommitCancelled, Freezer
-from .util import commit_container, container_is_running, stop_container
+from ..freeze import Freezer
+from .util import commit_container
 from ...log import info
 
 
 class MacosContainerFreezer(Freezer):
-    """Freezes a macOS-container bottle via `container export` + image rebuild."""
+    """Freezes a macOS-container bottle via exec-tar + image rebuild."""
 
     backend_name = "macos-container"
 
     def _freeze(self, agent: ActiveAgent) -> str:
         container = f"bot-bottle-{agent.slug}"
         image_tag = f"bot-bottle-committed-{agent.slug}:latest"
-        if container_is_running(container):
-            sys.stderr.write(
-                f"bot-bottle: bottle {agent.slug!r} is running; "
-                "commit will stop it. Continue? [y/N] "
-            )
-            sys.stderr.flush()
-            reply = _read_tty_line().strip().lower()
-            if reply not in ("y", "yes"):
-                raise CommitCancelled
-            stop_container(container)
         commit_container(container, image_tag)
         return image_tag
 
@@ -40,12 +29,3 @@ class MacosContainerFreezer(Freezer):
             f"to export for migration:      "
             f"container image save {image_ref} -o {slug}.tar"
         )
-
-
-def _read_tty_line() -> str:
-    """Read one line from /dev/tty, falling back to stdin."""
-    try:
-        with open("/dev/tty", "r", encoding="utf-8") as tty:
-            return tty.readline().rstrip("\n")
-    except OSError:
-        return sys.stdin.readline().rstrip("\n")