v0.20.3

Fixed

• README Quickstart (#139, found by running ach smoke on it): it now says what you need before the first command. That is Node.js 22+ and an agent CLI that is installed and signed in, with the Claude Code and Codex installs as commands you can copy. It explains that each ach run gives Claude Code a fresh config dir, so the examples pass --claude-default-config (or you set CLAUDE_CODE_OAUTH_TOKEN / ANTHROPIC_API_KEY). It also says ach web keeps running, so start it in its own terminal (--no-open skips the browser).
• ach smoke: spawn claude ENOENT is reported as a missing prerequisite that names the agent CLI, not as a bare failure. Friction evidence skips npm notice/warn lines. A command missing because an earlier Homebrew install was skipped (host-level) now says so, and no fix is planned for it.
• ach smoke: opening a loopback URL (127.x, localhost, [::1], 0.0.0.0) is never treated as a browser login. It is recorded as localUrls. A step that is still running after 8 s while listening on a TCP port (ach web, a dev server) passes as a service and is stopped at teardown, instead of failing on the step timeout.
• ach smoke: an agent CLI that runs but is not signed in ("Not logged in", "please run /login", "not authenticated") is auth-needs-human friction. A step that refuses to run outside a git repository (codex: "Not inside a trusted directory") is an unstated-assumption.
• ach smoke: the sandbox pre-creates .codex, because codex exits when CODEX_HOME points at a missing directory.

Fixes #139