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/provision/provider_auth.py

@@ -2,35 +2,34 @@
 
 from __future__ import annotations
 
-import subprocess
+import shlex
 
+from ....log import die
+from ... import Bottle
 from ..bottle_plan import DockerBottlePlan
 
 
-def provision_provider_auth(plan: DockerBottlePlan, target: str) -> None:
-    """Apply provider-owned guest setup through Docker primitives."""
+def provision_provider_auth(plan: DockerBottlePlan, bottle: Bottle) -> None:
+    """Apply provider-owned guest setup through the bottle's exec / cp_in."""
     provision = plan.agent_provision
     for d in provision.dirs:
-        _exec(target, ["mkdir", "-p", d.guest_path])
-        _exec(target, ["chown", d.owner, d.guest_path])
-        _exec(target, ["chmod", d.mode, d.guest_path])
+        _exec(bottle, f"mkdir -p {shlex.quote(d.guest_path)}", d.guest_path)
+        _exec(bottle, f"chown {shlex.quote(d.owner)} {shlex.quote(d.guest_path)}", d.guest_path)
+        _exec(bottle, f"chmod {shlex.quote(d.mode)} {shlex.quote(d.guest_path)}", d.guest_path)
     for command in provision.pre_copy:
-        _exec(target, list(command.argv))
+        _exec(bottle, shlex.join(command.argv), command.error)
     for f in provision.files:
-        subprocess.run(
-            ["docker", "cp", str(f.host_path), f"{target}:{f.guest_path}"],
-            stdout=subprocess.DEVNULL,
-            check=True,
-        )
-        _exec(target, ["chown", f.owner, f.guest_path])
-        _exec(target, ["chmod", f.mode, f.guest_path])
+        bottle.cp_in(str(f.host_path), f.guest_path)
+        _exec(bottle, f"chown {shlex.quote(f.owner)} {shlex.quote(f.guest_path)}", f.guest_path)
+        _exec(bottle, f"chmod {shlex.quote(f.mode)} {shlex.quote(f.guest_path)}", f.guest_path)
     for command in provision.verify:
-        _exec(target, list(command.argv))
+        _exec(bottle, shlex.join(command.argv), command.error)
 
 
-def _exec(target: str, argv: list[str]) -> None:
-    subprocess.run(
-        ["docker", "exec", "-u", "0", target, *argv],
-        stdout=subprocess.DEVNULL,
-        check=True,
-    )
+def _exec(bottle: Bottle, script: str, error: str) -> None:
+    result = bottle.exec(script, user="root")
+    if result.returncode != 0:
+        detail = (result.stderr or result.stdout).strip()
+        if detail:
+            detail = f": {detail}"
+        die(f"agent provider provisioning: {error}{detail}")