refactor(docker): split provision into provision_prompt / _ssh / _git

provision now orchestrates three focused sub-methods. Each sub-method
self-gates: provision_ssh is a no-op when the bottle has no SSH
entries; provision_git is a no-op when --cwd was not set. The prompt
copy + chown always runs (so the path always exists in-container);
the return is gated on whether the agent has a non-empty prompt.

claude_bottle/backend/docker/backend.py

@@ -269,6 +269,20 @@ class DockerBottleBackend(BottleBackend):
             f"got {type(plan).__name__}"
         )
         container = target
+
+        prompt_path = self.provision_prompt(plan, container)
+        agent = plan.spec.manifest.agents[plan.spec.agent_name]
+        if agent.skills:
+            skills_mod.skills_copy_into(container, list(agent.skills))
+        self.provision_ssh(plan, container)
+        self.provision_git(plan, container)
+        return prompt_path
+
+    def provision_prompt(self, plan: DockerBottlePlan, container: 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."""
         container_home = os.environ.get("CLAUDE_BOTTLE_CONTAINER_HOME", "/home/node")
         in_container_prompt_path = f"{container_home}/.claude-bottle-prompt.txt"
 
@@ -291,15 +305,24 @@ class DockerBottleBackend(BottleBackend):
         )
 
         agent = plan.spec.manifest.agents[plan.spec.agent_name]
-        if agent.skills:
+        return in_container_prompt_path if agent.prompt else None
-            skills_mod.skills_copy_into(container, list(agent.skills))
 
+    def provision_ssh(self, plan: DockerBottlePlan, container: str) -> None:
+        """If the bottle has SSH entries, set up the in-container
+        ssh-agent and config so node can authenticate without ever
+        seeing the key bytes. No-op when the bottle has no SSH."""
         bottle = plan.spec.manifest.bottle_for(plan.spec.agent_name)
-        if bottle.ssh:
+        if not bottle.ssh:
+            return
         proxy_host_port = pipelock.pipelock_proxy_host_port(plan.slug)
         ssh_mod.ssh_setup(container, plan.stage_dir, proxy_host_port, bottle.ssh)
 
-        if plan.spec.copy_cwd and Path(plan.spec.user_cwd, ".git").is_dir():
+    def provision_git(self, plan: DockerBottlePlan, container: str) -> None:
+        """If --cwd was set and the host cwd has a .git directory, copy
+        it into /home/node/workspace/.git and fix ownership. No-op
+        otherwise."""
+        if not (plan.spec.copy_cwd and Path(plan.spec.user_cwd, ".git").is_dir()):
+            return
         info(f"copying {plan.spec.user_cwd}/.git -> {container}:/home/node/workspace/.git")
         subprocess.run(
             ["docker", "cp", f"{plan.spec.user_cwd}/.git", f"{container}:/home/node/workspace/.git"],
@@ -315,8 +338,6 @@ class DockerBottleBackend(BottleBackend):
             check=True,
         )
 
-        return in_container_prompt_path if agent.prompt else None
-
     # --- Cleanup ---
 
     def prepare_cleanup(self) -> DockerBottleCleanupPlan: