41 — CLI Entry & arg0 Multitool Dispatch

目标 / Goal

Port codex-cli + codex-arg0: the main binary, the complete subcommand surface, top-level flags, and the busybox-style arg0 multitool dispatch.

reference-codex/codex-rs/cli/src/ (main.rs, lib.rs, *_cmd.rs, exit_status.rs).
reference-codex/codex-rs/arg0/src/lib.rs (argv0/argv1 dispatch, PATH symlink guard).
reference-codex/docs/getting-started.md.

Default (no subcommand) → TUI; full subcommand set wired (the rest land in spec 42 and their owning specs): exec/e, review, resume, fork, archive, unarchive, login/logout, mcp, mcp-server, app, app-server, remote-control, exec-server, cloud/cloud-tasks, plugin, marketplace, apply/a, doctor, sandbox, completion, update, features, debug …, responses-api-proxy, stdio-to-uds, execpolicy check, state-db-recovery.
Top-level flags: -c key=value (repeatable), -p/--profile, --enable/--disable (repeatable), --remote [ws://|wss://|unix://], --remote-auth-token-env, --strict-config. Propagate to subcommands like Codex (clap-flatten semantics; reject --remote on non-TUI subcommands).
arg0 dispatch: when invoked as codex-linux-sandbox, apply_patch/ applypatch, codex-execve-wrapper, route to the right entrypoint; argv[1] dispatch (FS_HELPER, apply-patch arg1). PATH symlink guard creating session-lifetime aliases.
Exit codes: exit_status conventions (signals 128+n on Unix; direct on Windows).
completion for bash/zsh/fish/powershell/elvish.

codexgo --help and every codexgo <cmd> --help present the same subcommands and flags as Codex (golden help-text comparison, modulo binary name).
arg0 dispatch: invoking the binary under each alias name runs the right tool (differential — e.g. apply_patch reads a patch from stdin and applies it).
Exit codes match Codex across representative success/failure/signal cases.
Shell completion scripts generate for all five shells.

cobra/pflag vs clap differ in help formatting and flag propagation; match the structure (names, arity, defaults) and document cosmetic help differences.
arg0 trick + PATH symlink guard must work across OSes (Windows has no symlinks in the same way — match Codex's Windows behavior).