refactor(backend): hoist guest_home to BottlePlan base

Per PR review feedback (review #132): guest_home shouldn't be
buried inside workspace_plan / read from a hardcoded literal in
each provision module. It's a cross-cutting bottle property — the
backend's prepare step knows it, and every downstream consumer
(contrib providers, git provisioning, gitconfig path) should
read it from one place.

- Adds guest_home: str to BottlePlan base dataclass.
- Both backends' prepare steps populate plan.guest_home.
- contrib/{claude,codex}/agent_provider.py read plan.guest_home
  (was plan.workspace_plan.guest_home).
- bot_bottle/backend/docker/provision/git.py reads plan.guest_home
  for the gitconfig destination (was hardcoded "/home/node").
- bot_bottle/backend/smolmachines/provision/git.py drops the
  _GUEST_HOME / _guest_home() helpers and reads plan.guest_home.
- Tests that construct BottlePlan subclasses directly pass
  guest_home="/home/node" explicitly.

bot_bottle/backend/__init__.py

@@ -76,6 +76,7 @@ class BottlePlan(ABC):
 
     spec: BottleSpec
     stage_dir: Path
+    guest_home: str
     git_gate_plan: GitGatePlan
     egress_plan: EgressPlan
     supervise_plan: SupervisePlan | None

bot_bottle/backend/docker/prepare.py

@@ -233,6 +233,7 @@ def resolve_plan(
     return DockerBottlePlan(
         spec=spec,
         stage_dir=stage_dir,
+        guest_home=guest_home,
         slug=slug,
         container_name=container_name,
         container_name_pinned=container_name_pinned,

bot_bottle/backend/docker/provision/git.py

@@ -57,7 +57,7 @@ def _provision_git_gate_config(plan: DockerBottlePlan, bottle: Bottle) -> None:
     manifest_bottle = plan.spec.manifest.bottle_for(plan.spec.agent_name)
     if not manifest_bottle.git:
         return
-    container_gitconfig = "/home/node/.gitconfig"
+    container_gitconfig = f"{plan.guest_home}/.gitconfig"
 
     content = git_gate_render_gitconfig(manifest_bottle.git, GIT_GATE_HOSTNAME)
     config_file = plan.stage_dir / "agent_gitconfig"

bot_bottle/backend/smolmachines/prepare.py

@@ -172,6 +172,7 @@ def resolve_plan(
     return SmolmachinesBottlePlan(
         spec=spec,
         stage_dir=stage_dir,
+        guest_home=guest_home,
         slug=slug,
         bundle_subnet=subnet,
         bundle_gateway=gateway,

bot_bottle/backend/smolmachines/provision/git.py

@@ -36,14 +36,6 @@ from ... import Bottle
 from ..bottle_plan import SmolmachinesBottlePlan
 
 
-# `node` is the agent user from the repo Dockerfile.
-_GUEST_HOME = "/home/node"
-
-
-def _guest_home() -> str:
-    return _GUEST_HOME
-
-
 def provision_git(plan: SmolmachinesBottlePlan, bottle: Bottle) -> None:
     """Set up git inside the guest. Runs all three subcases; each
     no-ops when its condition isn't met."""
@@ -92,7 +84,7 @@ def _provision_git_gate_config(
         manifest_bottle.git, plan.agent_git_gate_host, scheme="http",
     )
 
-    guest_gitconfig = f"{_guest_home()}/.gitconfig"
+    guest_gitconfig = f"{plan.guest_home}/.gitconfig"
     # Stage the file under the plan's stage_dir so cp_in
     # has a stable host path. The plan's stage_dir is cleaned up
     # by start.py's session-end teardown.

bot_bottle/contrib/claude/agent_provider.py

@@ -123,7 +123,7 @@ class ClaudeAgentProvider(AgentProvider):
         agent = plan.spec.manifest.agents[plan.spec.agent_name]
         if not agent.skills:
             return
-        skills_dir = _skills_dir(plan.workspace_plan.guest_home)
+        skills_dir = _skills_dir(plan.guest_home)
         bottle.exec(f"mkdir -p {skills_dir}", user="root")
         for name in agent.skills:
             src = host_skill_dir(name)
@@ -143,7 +143,7 @@ class ClaudeAgentProvider(AgentProvider):
         Returns the in-guest path iff the agent has a non-empty
         prompt (drives `--append-system-prompt-file`); the file is
         copied either way so the path always exists."""
-        prompt_path = _prompt_path(plan.workspace_plan.guest_home)
+        prompt_path = _prompt_path(plan.guest_home)
         bottle.cp_in(str(plan.prompt_file), prompt_path)
         bottle.exec(
             f"chown node:node {prompt_path} && chmod 600 {prompt_path}",

bot_bottle/contrib/codex/agent_provider.py

@@ -168,7 +168,7 @@ class CodexAgentProvider(AgentProvider):
         agent = plan.spec.manifest.agents[plan.spec.agent_name]
         if not agent.skills:
             return
-        skills_dir = _skills_dir(plan.workspace_plan.guest_home)
+        skills_dir = _skills_dir(plan.guest_home)
         bottle.exec(f"mkdir -p {skills_dir}", user="root")
         for name in agent.skills:
             src = host_skill_dir(name)
@@ -188,7 +188,7 @@ class CodexAgentProvider(AgentProvider):
         Codex reads it via the agent's `Read and follow the
         instructions in <path>.` bootstrap (see `prompt_args`); the
         file is copied either way so the path always exists."""
-        prompt_path = _prompt_path(plan.workspace_plan.guest_home)
+        prompt_path = _prompt_path(plan.guest_home)
         bottle.cp_in(str(plan.prompt_file), prompt_path)
         bottle.exec(
             f"chown node:node {prompt_path} && chmod 600 {prompt_path}",

tests/unit/test_compose.py

@@ -164,6 +164,7 @@ def _plan(
 
     spec = _spec(supervise=supervise, with_git=with_git, with_egress=with_egress)
     return DockerBottlePlan(
+        guest_home="/home/node",
         spec=spec,
         stage_dir=STAGE,
         slug=SLUG,

tests/unit/test_contrib_claude_provider.py

@@ -78,6 +78,7 @@ def _plan(
             current_config_dir=Path("/tmp/current-config"),
         )
     return DockerBottlePlan(
+        guest_home="/home/node",
         spec=spec,
         stage_dir=Path("/tmp/stage"),
         slug="demo-abc12",

tests/unit/test_contrib_codex_provider.py

@@ -78,6 +78,7 @@ def _plan(
             current_config_dir=Path("/tmp/current-config"),
         )
     return DockerBottlePlan(
+        guest_home="/home/node",
         spec=spec,
         stage_dir=Path("/tmp/stage"),
         slug="demo-abc12",

tests/unit/test_docker_launch_teardown.py

@@ -44,6 +44,7 @@ def _plan(tmp: str) -> DockerBottlePlan:
         identity="test-teardown-00001",
     )
     return DockerBottlePlan(
+        guest_home="/home/node",
         spec=spec,
         stage_dir=stage,
         git_gate_plan=GitGatePlan(

tests/unit/test_docker_provision_git_user.py

@@ -40,6 +40,7 @@ def _plan(*, git_user: dict | None = None,
         copy_cwd=copy_cwd, user_cwd=user_cwd,
     )
     return DockerBottlePlan(
+        guest_home="/home/node",
         spec=spec,
         stage_dir=stage_dir or Path("/tmp/stage"),
         slug="demo-abc12",

tests/unit/test_plan_print_parity.py

@@ -103,6 +103,7 @@ def _proxy_plan(tmp: str) -> PipelockProxyPlan:
 def _docker_plan(spec: BottleSpec, tmp: str) -> DockerBottlePlan:
     stage = Path(tmp)
     return DockerBottlePlan(
+        guest_home="/home/node",
         spec=spec,
         stage_dir=stage,
         git_gate_plan=_git_gate_plan(tmp),
@@ -128,6 +129,7 @@ def _docker_plan(spec: BottleSpec, tmp: str) -> DockerBottlePlan:
 def _smolmachines_plan(spec: BottleSpec, tmp: str) -> SmolmachinesBottlePlan:
     stage = Path(tmp)
     return SmolmachinesBottlePlan(
+        guest_home="/home/node",
         spec=spec,
         stage_dir=stage,
         git_gate_plan=_git_gate_plan(tmp),

tests/unit/test_smolmachines_provision.py

@@ -120,6 +120,7 @@ def _plan(
             current_config_dir=Path("/tmp/current-config"),
         )
     return SmolmachinesBottlePlan(
+        guest_home="/home/node",
         spec=spec,
         stage_dir=stage_dir or Path("/tmp/stage"),
         slug="demo-abc12",