Merge main into fix/db-off-data-plane-469

Brings in main's 8 commits — #470 (backend-agnostic CI guards: BackendStatus
enum, quiet status(), is_backend_available/is_backend_ready, tests/_backend.py
skip_unless_backend) plus firecracker status() readiness checks (kvm/kernel/
dropbear/mke2fs).

Reconciled #470's additions into the reorg'd backend structure:
  * BackendStatus enum + the status(*, quiet=) ABC signature -> backend/base.py
  * is_backend_available / is_backend_ready -> backend/selection.py
  * exposed all three through the lazy backend facade (__init__).
Integration-test conflicts were our control_plane->orchestrator renames vs
main's skip_unless_docker -> skip_unless_backend swap: kept our refactored
import paths + main's guard. Repointed main's new is_backend_* tests to patch
selection._backends (our moved home) instead of the facade.

pyright: 0 errors. Full unit suite green (2272).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bot_bottle/backend/selection.py

@@ -14,7 +14,7 @@ from typing import Any
 
 from ..log import die, info, warn
 from ..util import read_tty_line
-from .base import ActiveAgent, BottleBackend
+from .base import ActiveAgent, BackendStatus, BottleBackend
 
 
 # _backends is None until the first call to _get_backends(), at which
@@ -166,6 +166,29 @@ def has_backend(name: str) -> bool:
     return backends[name].is_available()
 
 
+def is_backend_available(name: str) -> bool:
+    """Cheap availability check: is the backend's binary on PATH?
+
+    Suitable for cleanup enumeration and auto-selection — does NOT probe
+    the daemon or network pool. Use is_backend_ready() for a full
+    readiness check before launching tests."""
+    return has_backend(name)
+
+
+def is_backend_ready(name: str, *, quiet: bool = False) -> bool:
+    """Full readiness check: passes all of the backend's status() checks.
+
+    When quiet=False the backend prints diagnostic output explaining what
+    is missing — intended for test-suite guards that run at discovery time
+    so the operator sees a concrete failure reason for each skip.
+
+    Returns False for unknown backend names."""
+    backends = _get_backends()
+    if name not in backends:
+        return False
+    return backends[name].status(quiet=quiet) == BackendStatus.READY
+
+
 def enumerate_active_agents() -> list[ActiveAgent]:
     """All currently-running agents, across every available
     backend. Used by CLI `active` and the dashboard's agents