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/smolmachines/provision/workspace.py

@@ -5,11 +5,11 @@ from __future__ import annotations
 import shlex
 
 from ....log import info
-from .. import smolvm as _smolvm
+from ... import Bottle
 from ..bottle_plan import SmolmachinesBottlePlan
 
 
-def provision_workspace(plan: SmolmachinesBottlePlan, target: str) -> None:
+def provision_workspace(plan: SmolmachinesBottlePlan, bottle: Bottle) -> None:
     """Copy host cwd contents to the planned guest workspace."""
     workspace = plan.workspace_plan
     if not (workspace.enabled and workspace.copy_contents):
@@ -20,17 +20,13 @@ def provision_workspace(plan: SmolmachinesBottlePlan, target: str) -> None:
     guest_parent_q = shlex.quote(guest_parent)
     owner_q = shlex.quote(workspace.owner)
     mode_q = shlex.quote(workspace.mode)
-    info(f"copying {workspace.host_path} -> {target}:{workspace.guest_path}")
-    _smolvm.machine_exec(
-        target,
-        ["sh", "-c", f"rm -rf {guest_path_q} && mkdir -p {guest_parent_q}"],
+    info(f"copying {workspace.host_path} -> {bottle.name}:{workspace.guest_path}")
+    bottle.exec(
+        f"rm -rf {guest_path_q} && mkdir -p {guest_parent_q}",
+        user="root",
     )
-    _smolvm.machine_cp(str(workspace.host_path), f"{target}:{workspace.guest_path}")
-    _smolvm.machine_exec(
-        target,
-        [
-            "sh", "-c",
-            f"chown -R {owner_q} {guest_path_q} && "
-            f"chmod {mode_q} {guest_path_q}",
-        ],
+    bottle.cp_in(str(workspace.host_path), workspace.guest_path)
+    bottle.exec(
+        f"chown -R {owner_q} {guest_path_q} && chmod {mode_q} {guest_path_q}",
+        user="root",
     )