refactor(agent_provider): introduce AgentProvider ABC + contrib plugins

Lift the provider-specific blocks of agent_provision_plan into
contrib/claude/agent_provider.py and contrib/codex/agent_provider.py,
behind a new AgentProvider ABC and a lazy get_provider() registry
(mirrors PRD 0048's contrib convention).

agent_provision_plan and runtime_for stay as thin shims so existing
callers in backend/{docker,smolmachines}/prepare.py and cli/start.py
keep working without per-call edits — the shipping diff in this commit
is purely 'who owns the producer'.

Adds bot_bottle/_provision_apply.py — the backend-agnostic
skills / prompt / declarative-plan apply loops the per-provider
default methods will dispatch through in the next commit.

bot_bottle/contrib/codex/agent_provider.py

@@ -0,0 +1,175 @@
+"""Codex agent provider plugin (PRD 0050, contrib).
+
+The Codex-specific behavior previously inlined under
+`agent_provider.agent_provision_plan` (config.toml trust marker,
+chatgpt.com / api.openai.com egress routes, optional host-credential
+forwarding with dummy-auth.json + verify), plus the `codex mcp add`
+invocation that registers the supervise sidecar in Codex's
+~/.codex/config.toml (PRD 0050)."""
+
+from __future__ import annotations
+
+import os
+from pathlib import Path
+from typing import TYPE_CHECKING
+
+from ...agent_provider import (
+    CODEX_HOST_CREDENTIAL_HOSTS,
+    GUEST_HOME,
+    AgentProvider,
+    AgentProviderRuntime,
+    AgentProvisionCommand,
+    AgentProvisionDir,
+    AgentProvisionFile,
+    AgentProvisionPlan,
+)
+from ...codex_auth import codex_host_access_token, write_codex_dummy_auth_file
+from ...egress import CODEX_HOST_CREDENTIAL_TOKEN_REF, EgressRoute
+from ...log import info, warn
+
+
+if TYPE_CHECKING:
+    from ...backend import Bottle, BottlePlan
+
+
+_REPO_ROOT = Path(__file__).resolve().parents[3]
+
+_SUPERVISE_MCP_NAME = "supervise"
+
+_RUNTIME = AgentProviderRuntime(
+    template="codex",
+    command="codex",
+    image="bot-bottle-codex:latest",
+    dockerfile=str(_REPO_ROOT / "Dockerfile.codex"),
+    prompt_mode="read_prompt_file",
+    bypass_args=("--dangerously-bypass-approvals-and-sandbox",),
+    resume_args=("resume", "--last"),
+    remote_control_args=(),
+)
+
+
+class CodexAgentProvider(AgentProvider):
+    @property
+    def runtime(self) -> AgentProviderRuntime:
+        return _RUNTIME
+
+    def provision_plan(
+        self,
+        *,
+        dockerfile: str,
+        state_dir: Path,
+        guest_home: str = GUEST_HOME,
+        guest_env: dict[str, str] | None = None,
+        auth_token: str = "",
+        forward_host_credentials: bool = False,
+        host_env: dict[str, str] | None = None,
+        trusted_project_path: str = "",
+    ) -> AgentProvisionPlan:
+        del auth_token  # Claude-only knob
+        resolved_guest_env = dict(guest_env or {})
+        trusted_path = trusted_project_path or guest_home
+
+        env_vars: dict[str, str] = {
+            "CODEX_CA_CERTIFICATE": "/etc/ssl/certs/ca-certificates.crt",
+        }
+        auth_dir = resolved_guest_env.get("CODEX_HOME", f"{guest_home}/.codex")
+        if forward_host_credentials:
+            env_vars["CODEX_HOME"] = auth_dir
+
+        dirs = [AgentProvisionDir(auth_dir)]
+        files: list[AgentProvisionFile] = []
+        pre_copy: list[AgentProvisionCommand] = []
+        verify: list[AgentProvisionCommand] = []
+        provisioned_env: dict[str, str] = {}
+
+        config_path = f"{auth_dir}/config.toml"
+        config_file = state_dir / "codex-config.toml"
+        toml_path = trusted_path.replace("\\", "\\\\").replace('"', '\\"')
+        config_file.write_text(
+            f'[projects."{toml_path}"]\n'
+            'trust_level = "trusted"\n'
+        )
+        config_file.chmod(0o600)
+        files.append(AgentProvisionFile(config_file, config_path))
+
+        egress_routes: list[EgressRoute] = []
+        for host in CODEX_HOST_CREDENTIAL_HOSTS:
+            egress_routes.append(EgressRoute(
+                host=host,
+                auth_scheme="Bearer" if forward_host_credentials else "",
+                token_ref=CODEX_HOST_CREDENTIAL_TOKEN_REF if forward_host_credentials else "",
+                tls_passthrough=True,
+            ))
+
+        if forward_host_credentials:
+            _host_env = host_env or dict(os.environ)
+            provisioned_env[CODEX_HOST_CREDENTIAL_TOKEN_REF] = (
+                codex_host_access_token(_host_env)
+            )
+            auth_file = state_dir / "codex-auth.json"
+            write_codex_dummy_auth_file(auth_file, _host_env)
+            files.append(AgentProvisionFile(auth_file, f"{auth_dir}/auth.json"))
+            pre_copy.append(AgentProvisionCommand((
+                "find", auth_dir,
+                "-maxdepth", "1",
+                "-type", "f",
+                "(",
+                "-name", "*.sqlite",
+                "-o", "-name", "*.sqlite-*",
+                "-o", "-name", "*.codex-repair-*.bak",
+                ")",
+                "-delete",
+            ), "codex host credentials: could not reset runtime db files"))
+            verify.append(AgentProvisionCommand((
+                "runuser", "-u", "node", "--",
+                "env",
+                f"HOME={guest_home}",
+                f"CODEX_HOME={auth_dir}",
+                "codex", "login", "status",
+            ), (
+                "codex host credentials: dummy auth was copied into the "
+                "guest, but Codex did not accept it"
+            )))
+
+        return AgentProvisionPlan(
+            template=_RUNTIME.template,
+            command=_RUNTIME.command,
+            prompt_mode=_RUNTIME.prompt_mode,
+            image=_RUNTIME.image,
+            dockerfile=dockerfile,
+            env_vars=env_vars,
+            guest_env=resolved_guest_env,
+            dirs=tuple(dirs),
+            files=tuple(files),
+            pre_copy=tuple(pre_copy),
+            verify=tuple(verify),
+            egress_routes=tuple(egress_routes),
+            provisioned_env=provisioned_env,
+        )
+
+    def provision_supervise_mcp(
+        self,
+        plan: "BottlePlan",
+        bottle: "Bottle",
+        supervise_url: str,
+    ) -> None:
+        """Run `codex mcp add` inside the agent guest to register the
+        supervise sidecar in Codex's user config (~/.codex/config.toml).
+
+        Mirrors the Claude provider's `claude mcp add` flow — failure
+        is logged but not fatal."""
+        if plan.supervise_plan is None:
+            return
+        info(f"registering supervise MCP server in agent codex config → {supervise_url}")
+        r = bottle.exec(
+            f"codex mcp add --transport http "
+            f"{_SUPERVISE_MCP_NAME} {supervise_url}",
+            user="node",
+        )
+        if r.returncode != 0:
+            warn(
+                f"`codex mcp add supervise` failed (exit {r.returncode}): "
+                f"{(r.stderr or r.stdout or '').strip()}. Inside the bottle, "
+                f"register manually with: "
+                f"codex mcp add --transport http supervise {supervise_url}"
+            )