refactor(docker): share derive step between print and to_dict

DockerBottlePlan.print and .to_dict each pulled the same agent /
bottle / env_names / ssh_hosts / prompt-first-line out of the spec
before formatting. Extract a private _view() helper that returns a
small frozen _PlanView dataclass with those derived fields; both
methods consume it. Removes the duplicated derivation and the risk
that one renderer drifts from the other (the OAuth-name append in
particular existed twice).

claude_bottle/backend/docker/bottle_plan.py

@@ -12,10 +12,23 @@ from dataclasses import dataclass
 from pathlib import Path
 
 from ...log import info
+from ...manifest import Agent, Bottle
 from ...pipelock import PipelockProxyPlan, pipelock_effective_allowlist
 from .. import BottlePlan
 
 
+@dataclass(frozen=True)
+class _PlanView:
+    """Fields that both `print` and `to_dict` need but the plan
+    doesn't store directly. Cheap to compute; computed once per call."""
+
+    agent: Agent
+    bottle: Bottle
+    env_names: list[str]
+    ssh_hosts: list[str]
+    prompt_first_line: str
+
+
 @dataclass(frozen=True)
 class DockerBottlePlan(BottlePlan):
     """Docker-specific resolved fields produced by
@@ -35,19 +48,26 @@ class DockerBottlePlan(BottlePlan):
     allowlist_summary: str
     use_runsc: bool
 
-    def print(self, *, remote_control: bool) -> None:
-        """Render the y/N preflight summary to stderr. Pure presentation."""
+    def _view(self) -> _PlanView:
         spec = self.spec
         manifest = spec.manifest
         agent = manifest.agents[spec.agent_name]
         bottle = manifest.bottle_for(spec.agent_name)
-
         env_names = list(bottle.env.keys())
         if spec.forward_oauth_token:
             env_names.append("CLAUDE_CODE_OAUTH_TOKEN")
+        return _PlanView(
+            agent=agent,
+            bottle=bottle,
+            env_names=env_names,
+            ssh_hosts=[e.Host for e in bottle.ssh],
+            prompt_first_line=agent.prompt.splitlines()[0] if agent.prompt else "",
+        )
 
-        ssh_hosts = [e.Host for e in bottle.ssh]
-        prompt_first_line = agent.prompt.splitlines()[0] if agent.prompt else ""
+    def print(self, *, remote_control: bool) -> None:
+        """Render the y/N preflight summary to stderr. Pure presentation."""
+        v = self._view()
+        spec = self.spec
         runtime_label = "runsc (gVisor)" if self.use_runsc else "runc (default)"
 
         print(file=sys.stderr)
@@ -60,51 +80,43 @@ class DockerBottlePlan(BottlePlan):
             )
         info(f"container       : {self.container_name}")
         info(f"stage dir       : {self.stage_dir}")
-        info("env (names only): " + (", ".join(env_names) if env_names else "(none)"))
-        info("skills          : " + (" ".join(agent.skills) if agent.skills else "(none)"))
+        info("env (names only): " + (", ".join(v.env_names) if v.env_names else "(none)"))
+        info("skills          : " + (" ".join(v.agent.skills) if v.agent.skills else "(none)"))
         info(f"docker runtime  : {runtime_label}")
-        info(f"bottle             : {agent.bottle}")
-        if ssh_hosts:
-            info(f"  ssh hosts     : {', '.join(ssh_hosts)}")
+        info(f"bottle             : {v.agent.bottle}")
+        if v.ssh_hosts:
+            info(f"  ssh hosts     : {', '.join(v.ssh_hosts)}")
         else:
             info("  ssh hosts     : (none)")
         info(f"  egress        : {self.allowlist_summary}")
         info(
-            f"prompt          : {len(agent.prompt)} chars; "
-            f"first line: {prompt_first_line or '(empty)'}"
+            f"prompt          : {len(v.agent.prompt)} chars; "
+            f"first line: {v.prompt_first_line or '(empty)'}"
         )
         info("remote-control  : " + ("enabled" if remote_control else "disabled"))
         print(file=sys.stderr)
 
     def to_dict(self, *, remote_control: bool) -> dict[str, object]:
-        spec = self.spec
-        manifest = spec.manifest
-        agent = manifest.agents[spec.agent_name]
-        bottle = manifest.bottle_for(spec.agent_name)
-
-        env_names = list(bottle.env.keys())
-        if spec.forward_oauth_token:
-            env_names.append("CLAUDE_CODE_OAUTH_TOKEN")
-
-        hosts = pipelock_effective_allowlist(bottle)
+        v = self._view()
+        hosts = pipelock_effective_allowlist(v.bottle)
         return {
-            "agent": spec.agent_name,
-            "bottle": agent.bottle,
+            "agent": self.spec.agent_name,
+            "bottle": v.agent.bottle,
             "container_name": self.container_name,
             "image": self.image,
             "derived_image": self.derived_image,
             "stage_dir": str(self.stage_dir),
             "runtime": "runsc" if self.use_runsc else "runc",
-            "env_names": env_names,
-            "skills": list(agent.skills),
-            "ssh_hosts": [e.Host for e in bottle.ssh],
+            "env_names": v.env_names,
+            "skills": list(v.agent.skills),
+            "ssh_hosts": v.ssh_hosts,
             "egress": {
                 "host_count": len(hosts),
                 "hosts": hosts,
             },
             "prompt": {
-                "length": len(agent.prompt),
-                "first_line": agent.prompt.splitlines()[0] if agent.prompt else "",
+                "length": len(v.agent.prompt),
+                "first_line": v.prompt_first_line,
             },
             "remote_control": remote_control,
         }