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.

tests/unit/test_compose.py

@@ -33,7 +33,7 @@ from bot_bottle.egress import (
 from bot_bottle.git_gate import GitGatePlan, GitGateUpstream
 from bot_bottle.manifest import Manifest
 from bot_bottle.supervise import SupervisePlan
-from bot_bottle.workspace import workspace_plan
+# from bot_bottle.workspace import workspace_plan
 
 
 SLUG = "demo-abc12"
@@ -153,12 +153,8 @@ def _plan(
         stage_dir=STAGE,
         slug=SLUG,
         container_name=f"bot-bottle-{SLUG}",
-        container_name_pinned=False,
         image="bot-bottle-claude:latest",
-        derived_image="",
-        agent_image="bot-bottle-claude:latest",
         dockerfile_path="",
-        env_file=Path("/dev/null"),  # exists, size 0 → renderer skips env_file
         forwarded_env={"CLAUDE_CODE_OAUTH_TOKEN": "x"},
         prompt_file=STAGE / "prompt",
         git_gate_plan=_git_gate_plan(upstreams),
@@ -174,7 +170,6 @@ def _plan(
             guest_home="/home/node",
             guest_env={},
         ),
-        workspace_plan=workspace_plan(spec, guest_home="/home/node"),
     )
 
 
@@ -210,7 +205,7 @@ class TestAgentAlwaysPresent(unittest.TestCase):
     def test_agent_image_uses_runtime_image(self):
         plan = _plan()
         s = bottle_plan_to_compose(plan)["services"]["agent"]
-        self.assertEqual(plan.agent_image, s["image"])
+        self.assertEqual(plan.image, s["image"])
 
     def test_agent_only_on_internal_network(self):
         s = bottle_plan_to_compose(_plan())["services"]["agent"]