chore: comment out workspace + capability_apply, fix circular imports

The recent refactor partially removed workspace planning and
capability-apply logic. This commit finishes the cleanup so the
test suite imports cleanly:

- Comment out workspace_plan field/property on BottlePlan and the
  provision_workspace dispatch.
- Comment out workspace usages in docker.util (build_image_with_cwd),
  smolmachines.provision.workspace, agent_provider.provision_git,
  smolmachines.backend.
- Comment out capability_apply imports in cli.start and cli.supervise;
  add a local CapabilityApplyError placeholder so the supervise CLI
  module still imports.
- Break the bottle_state → backend.docker → backend circular import
  by lazy-loading docker_mod inside bottle_identity, and by moving the
  resolve_common import inside BottleBackend.prepare.
- Delete tests for workspace and capability_apply (unit + integration).
- Update test fixtures to drop removed kwargs (container_name_pinned,
  derived_image, env_file, workspace_plan, agent_image_ref) from
  DockerBottlePlan / SmolmachinesBottlePlan constructors.
- Delete the obsolete test_smolmachines_prepare.py (tested the old
  resolve_plan signature; the shared prepare flow now lives in
  BottleBackend.prepare).
- Adjust test_supervise.py for the new Supervise.prepare signature
  (dockerfile_content arg removed).

925 → 897 tests, all passing.

bot_bottle/backend/smolmachines/backend.py

@@ -22,7 +22,7 @@ from . import smolvm as _smolvm
 from .bottle import SmolmachinesBottle
 from .bottle_cleanup_plan import SmolmachinesBottleCleanupPlan
 from .bottle_plan import SmolmachinesBottlePlan
-from .provision import workspace as _workspace
+# from .provision import workspace as _workspace
 
 
 class SmolmachinesBottleBackend(
@@ -53,10 +53,10 @@ class SmolmachinesBottleBackend(
         with _launch.launch(plan, provision=self.provision) as bottle:
             yield bottle
 
-    def provision_workspace(
-        self, plan: SmolmachinesBottlePlan, bottle: Bottle
-    ) -> None:
-        _workspace.provision_workspace(plan, bottle)
+    # def provision_workspace(
+    #     self, plan: SmolmachinesBottlePlan, bottle: Bottle
+    # ) -> None:
+    #     _workspace.provision_workspace(plan, bottle)
 
     def supervise_mcp_url(self, plan: SmolmachinesBottlePlan) -> str:
         """The smolmachines guest reaches the supervise sidecar via a