refactor(docker): move provision_prompt into provision/prompt.py

claude_bottle/backend/docker/backend.py

@@ -35,6 +35,7 @@ from .pipelock import (
     pipelock_proxy_host_port,
     pipelock_proxy_url,
 )
+from .provision import prompt as _prompt
 
 
 # Where the repo root lives, for `docker build` context. Computed once.
@@ -282,35 +283,8 @@ class DockerBottleBackend(BottleBackend):
             info(f"name conflict; retrying as {container}")
 
     def provision_prompt(self, plan: BottlePlan, target: str) -> str | None:
-        """Copy the prompt file into the container, fix ownership/mode.
-        Returns the in-container path if the agent has a non-empty
-        prompt (drives --append-system-prompt-file), else None. The
-        file is copied either way so the path always exists."""
         assert isinstance(plan, DockerBottlePlan)
-        container = target
-        container_home = os.environ.get("CLAUDE_BOTTLE_CONTAINER_HOME", "/home/node")
-        in_container_prompt_path = f"{container_home}/.claude-bottle-prompt.txt"
-
-        subprocess.run(
-            ["docker", "cp", str(plan.prompt_file), f"{container}:{in_container_prompt_path}"],
-            stdout=subprocess.DEVNULL,
-            check=True,
-        )
-        # `docker cp` preserves host UID; re-own/mode as root so node
-        # can read its own mode-600 prompt regardless of host UID.
-        subprocess.run(
-            ["docker", "exec", "-u", "0", container, "chown", "node:node", in_container_prompt_path],
-            stdout=subprocess.DEVNULL,
-            check=True,
-        )
-        subprocess.run(
-            ["docker", "exec", "-u", "0", container, "chmod", "600", in_container_prompt_path],
-            stdout=subprocess.DEVNULL,
-            check=True,
-        )
-
-        agent = plan.spec.manifest.agents[plan.spec.agent_name]
-        return in_container_prompt_path if agent.prompt else None
+        return _prompt.provision_prompt(plan, target)
 
     def validate_skills(self, skills: list[str]) -> None:
         """Fail loudly if any named skill is missing from the host's