feat(cleanup): walk every backend, reap smolmachines orphans too

`./cli.py cleanup` previously called only the env-var-selected
backend's `prepare_cleanup` / `cleanup` — so a leftover smolvm
machine + bundle container + bundle network from a crashed
smolmachines bottle would survive a default `docker`-mode cleanup
indefinitely.

Smolmachines now has a real `cleanup` module (alongside
`enumerate.py` from issue #77) that walks:

  - smolvm machines named `claude-bottle-*` (via
    `smolvm machine ls --json`)
  - bundle containers `claude-bottle-sidecars-*`
  - bundle networks `claude-bottle-bundle-*`

Cleanup runs stop+delete on the machines, force-rm on the
containers, network rm on the networks. Each step is best-effort
so a failed rm doesn't block the rest.

`cli.py cleanup` walks every backend in `known_backend_names()`
and runs each backend's `cleanup` after a single y/N prompt that
shows a combined plan.

State dirs (`~/.claude-bottle/state/<slug>/`) are shared layout
with the docker backend, which still owns the orphan-state-dir
bucket. It now consults `enumerate_active_bottles()` for the
cross-backend live identity set so a running smolmachines
bottle's state dir isn't reaped during a cleanup.

Tests: smolmachines cleanup (prepare + cleanup ordering + failure
handling); cross-backend orphan protection on the docker
state-dir check; CLI cmd_cleanup walks both backends, short-
circuits on all-empty, aborts on N. 617 unit tests pass.

End-to-end verified on this host:
  $ smolvm machine ls --json | jq '.[].name'
  "claude-bottle-researcher-m3hxd"
  $ ./cli.py cleanup
  --- smolmachines backend ---
  smolvm machine:  claude-bottle-researcher-m3hxd
  remove all of the above? [y/N]

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/unit/test_cli_cleanup_cross_backend.py

@@ -0,0 +1,105 @@
+"""Unit: `cli.py cleanup` walks every backend (issue follow-up).
+
+Asserts cmd_cleanup queries each backend's `prepare_cleanup`,
+combines the y/N output, and runs each backend's `cleanup` when
+the operator confirms.  Mocks the backends and stdin."""
+
+from __future__ import annotations
+
+import sys
+import unittest
+from unittest.mock import patch, MagicMock
+
+from claude_bottle.cli import cleanup as cmd
+
+
+def _make_backend(empty: bool = True):
+    backend = MagicMock()
+    plan = MagicMock(empty=empty)
+    backend.prepare_cleanup.return_value = plan
+    backend.cleanup = MagicMock()
+    return backend, plan
+
+
+class TestCmdCleanup(unittest.TestCase):
+    def test_iterates_every_backend(self):
+        docker, docker_plan = _make_backend(empty=False)
+        smol, smol_plan = _make_backend(empty=False)
+        backends_by_name = {"docker": docker, "smolmachines": smol}
+
+        with patch.object(
+            cmd, "known_backend_names",
+            return_value=("docker", "smolmachines"),
+        ), patch.object(
+            cmd, "get_bottle_backend",
+            side_effect=lambda name: backends_by_name[name],
+        ), patch.object(
+            cmd, "_prompt_yes", return_value=True,
+        ):
+            self.assertEqual(0, cmd.cmd_cleanup([]))
+
+        docker.prepare_cleanup.assert_called_once()
+        smol.prepare_cleanup.assert_called_once()
+        docker.cleanup.assert_called_once_with(docker_plan)
+        smol.cleanup.assert_called_once_with(smol_plan)
+
+    def test_short_circuits_when_all_empty(self):
+        docker, _ = _make_backend(empty=True)
+        smol, _ = _make_backend(empty=True)
+        backends_by_name = {"docker": docker, "smolmachines": smol}
+
+        with patch.object(
+            cmd, "known_backend_names",
+            return_value=("docker", "smolmachines"),
+        ), patch.object(
+            cmd, "get_bottle_backend",
+            side_effect=lambda name: backends_by_name[name],
+        ), patch.object(
+            cmd, "_prompt_yes",
+        ) as prompt:
+            self.assertEqual(0, cmd.cmd_cleanup([]))
+        prompt.assert_not_called()
+        docker.cleanup.assert_not_called()
+        smol.cleanup.assert_not_called()
+
+    def test_abort_at_prompt_runs_nothing(self):
+        docker, _ = _make_backend(empty=False)
+        smol, _ = _make_backend(empty=True)
+        backends_by_name = {"docker": docker, "smolmachines": smol}
+
+        with patch.object(
+            cmd, "known_backend_names",
+            return_value=("docker", "smolmachines"),
+        ), patch.object(
+            cmd, "get_bottle_backend",
+            side_effect=lambda name: backends_by_name[name],
+        ), patch.object(
+            cmd, "_prompt_yes", return_value=False,
+        ):
+            self.assertEqual(0, cmd.cmd_cleanup([]))
+        docker.cleanup.assert_not_called()
+        smol.cleanup.assert_not_called()
+
+    def test_skips_empty_plans_when_others_have_work(self):
+        # docker has work, smolmachines doesn't — only docker.cleanup
+        # is called.
+        docker, docker_plan = _make_backend(empty=False)
+        smol, _ = _make_backend(empty=True)
+        backends_by_name = {"docker": docker, "smolmachines": smol}
+
+        with patch.object(
+            cmd, "known_backend_names",
+            return_value=("docker", "smolmachines"),
+        ), patch.object(
+            cmd, "get_bottle_backend",
+            side_effect=lambda name: backends_by_name[name],
+        ), patch.object(
+            cmd, "_prompt_yes", return_value=True,
+        ):
+            cmd.cmd_cleanup([])
+        docker.cleanup.assert_called_once_with(docker_plan)
+        smol.cleanup.assert_not_called()
+
+
+if __name__ == "__main__":
+    unittest.main()