refactor(backend): pass Bottle to provisioners instead of target string

Closes #178.

The backend provision functions now receive a Bottle handle with
exec / cp_in methods instead of a raw target string. Provisioner
modules use bottle.exec and bottle.cp_in in place of inlined
subprocess.run(["docker", "exec"/"cp", ...]) and direct
_smolvm.machine_cp / machine_exec calls. This decouples the
provisioners from backend-specific runtime primitives so future
refactors (e.g. the supervise rework) can swap the bottle's exec
implementation without touching every provisioner.

Each launch.py constructs the Bottle handle before calling
provision so it can be passed in; provision_prompt's return value
is wired back onto the bottle's prompt path attribute after the
fact.

bot_bottle/backend/docker/backend.py

@@ -18,7 +18,7 @@ from contextlib import contextmanager
 from pathlib import Path
 from typing import Generator, Sequence
 
-from .. import ActiveAgent, BottleBackend, BottleSpec
+from .. import ActiveAgent, Bottle, BottleBackend, BottleSpec
 from . import cleanup as _cleanup
 from . import enumerate as _enumerate
 from . import launch as _launch
@@ -57,23 +57,23 @@ class DockerBottleBackend(BottleBackend["DockerBottlePlan", "DockerBottleCleanup
         with _launch.launch(plan, provision=self.provision) as bottle:
             yield bottle
 
-    def provision_ca(self, plan: DockerBottlePlan, target: str) -> None:
-        _ca.provision_ca(plan, target)
+    def provision_ca(self, plan: DockerBottlePlan, bottle: Bottle) -> None:
+        _ca.provision_ca(plan, bottle)
 
-    def provision_prompt(self, plan: DockerBottlePlan, target: str) -> str | None:
-        return _prompt.provision_prompt(plan, target)
+    def provision_prompt(self, plan: DockerBottlePlan, bottle: Bottle) -> str | None:
+        return _prompt.provision_prompt(plan, bottle)
 
-    def provision_provider_auth(self, plan: DockerBottlePlan, target: str) -> None:
-        _provider_auth.provision_provider_auth(plan, target)
+    def provision_provider_auth(self, plan: DockerBottlePlan, bottle: Bottle) -> None:
+        _provider_auth.provision_provider_auth(plan, bottle)
 
-    def provision_skills(self, plan: DockerBottlePlan, target: str) -> None:
-        _skills.provision_skills(plan, target)
+    def provision_skills(self, plan: DockerBottlePlan, bottle: Bottle) -> None:
+        _skills.provision_skills(plan, bottle)
 
-    def provision_git(self, plan: DockerBottlePlan, target: str) -> None:
-        _git.provision_git(plan, target)
+    def provision_git(self, plan: DockerBottlePlan, bottle: Bottle) -> None:
+        _git.provision_git(plan, bottle)
 
-    def provision_supervise(self, plan: DockerBottlePlan, target: str) -> None:
-        _supervise_prov.provision_supervise(plan, target)
+    def provision_supervise(self, plan: DockerBottlePlan, bottle: Bottle) -> None:
+        _supervise_prov.provision_supervise(plan, bottle)
 
     def prepare_cleanup(self) -> DockerBottleCleanupPlan:
         return _cleanup.prepare_cleanup()