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>

claude_bottle/backend/docker/cleanup.py

@@ -83,11 +83,18 @@ def _list_prefixed_networks() -> list[str]:
     return sorted(set(out))
 
 
-def _list_orphan_state_dirs(live_projects: set[str]) -> list[str]:
+def _list_orphan_state_dirs(
+    live_projects: set[str], protected_identities: set[str],
+) -> list[str]:
     """State identities whose compose project isn't running and
     that don't have a `.preserve` marker. `.preserve` means the
     user (or an auto-preserve-on-crash) wants the state kept for
-    `resume`."""
+    `resume`.
+
+    `protected_identities` is the set of slugs that are live in
+    ANY backend — used so this docker-side check doesn't reap a
+    running smolmachines bottle's state dir (the layout is shared
+    across both backends)."""
     state_root = _supervise.claude_bottle_root() / "state"
     if not state_root.is_dir():
         return []
@@ -99,6 +106,8 @@ def _list_orphan_state_dirs(live_projects: set[str]) -> list[str]:
         project = f"{COMPOSE_PROJECT_PREFIX}{identity}"
         if project in live_projects:
             continue
+        if identity in protected_identities:
+            continue
         if is_preserved(identity):
             continue
         orphans.append(identity)
@@ -106,15 +115,25 @@ def _list_orphan_state_dirs(live_projects: set[str]) -> list[str]:
 
 
 def prepare_cleanup() -> DockerBottleCleanupPlan:
-    """Enumerate everything cleanup will touch. No removals."""
+    """Enumerate everything cleanup will touch. No removals.
+
+    Pulls the union of live identities across backends via
+    `enumerate_active_agents()` so the orphan-state-dir bucket
+    doesn't include slugs whose smolmachines VM is still up."""
     docker_mod.require_docker()
     projects = list_compose_projects()
     project_set = set(projects)
+    # Late import to avoid a circular at module-load time —
+    # the backend package's __init__ imports this module.
+    from .. import enumerate_active_agents
+    protected = {a.slug for a in enumerate_active_agents()}
     return DockerBottleCleanupPlan(
         projects=tuple(projects),
         stray_containers=tuple(_list_prefixed_containers()),
         stray_networks=tuple(_list_prefixed_networks()),
-        orphan_state_dirs=tuple(_list_orphan_state_dirs(project_set)),
+        orphan_state_dirs=tuple(
+            _list_orphan_state_dirs(project_set, protected),
+        ),
     )