refactor: move bottle_state.py to top-level bot_bottle package

Both docker and smolmachines backends use bottle state helpers.
Moving to bot_bottle/ makes the sharing explicit and removes the
cross-backend dependency (smolmachines importing from ..docker).

All callers updated: docker backend, smolmachines backend, cli
modules, and tests.

bot_bottle/backend/docker/resolve_plan.py

@@ -25,7 +25,7 @@ from ...workspace import workspace_plan as resolve_workspace_plan
 from .. import BottleSpec
 from . import util as docker_mod
 from .bottle_plan import DockerBottlePlan
-from .bottle_state import (
+from ...bottle_state import (
     BottleMetadata,
     agent_state_dir,
     bottle_identity,