fix: restore backend prepare wiring

bot_bottle/backend/smolmachines/backend.py

@@ -46,6 +46,12 @@ class SmolmachinesBottleBackend(
         runtime check happens at `prepare`."""
         return _smolvm.is_available()
 
+    def _preflight(self) -> None:
+        _resolve_plan.preflight()
+
+    def _build_guest_env(self, resolved_env: ResolvedEnv) -> dict[str, str]:
+        return _resolve_plan.build_guest_env(resolved_env)
+
     def _resolve_plan(
         self,
         spec: BottleSpec,

bot_bottle/backend/smolmachines/resolve_plan.py

@@ -23,10 +23,11 @@ from ...git_gate import GitGatePlan
 from .bottle_plan import SmolmachinesBottlePlan
 from .util import smolmachines_bundle_subnet, smolmachines_preflight
 
-def preflight():
+def preflight() -> None:
     smolmachines_preflight()
 
-def build_guest_env(resolved_env: ResolvedEnv):
+
+def build_guest_env(resolved_env: ResolvedEnv) -> dict[str, str]:
     # Agent's env: resolve through resolve_env() so ?prompt entries
     # are prompted and ${HOST_VAR} entries are interpolated — matching
     # the Docker backend's contract. Forwarded (secret/interpolated)