Ask each agent whether it is logged in, without spending a request

[pathscale]

Answers "is each of the three agents logged in?", which previously had no clean answer: a missing login was only discoverable by running a turn and catching Error::NotAuthenticated, which costs quota and is a poor way to populate a settings screen.

for agent in Agent::ALL {
    let status = AuthStatus::check(agent).await?;
    println!("{agent}: {}", status.summary());
}

Real output from the live test:

claude-code: logged in as claude@pathscale.com (max)
codex:       logged in as ChatGPT
copilot:     unknown: copilot exposes no status command, so this cannot be
             confirmed without spending a request

What each CLI actually offers

	Command	Shape
Claude	claude auth status --json	JSON: loggedIn, authMethod, email, subscriptionType
Codex	codex login status	prose: "Logged in using ChatGPT"
Copilot	none	—

Two details worth flagging:

• Codex needs the negative matched first, since not logged in contains logged in. Tested against all three phrasings.
• Copilot reports Unknown, never LoggedOut. Telling someone to re-authenticate a working setup is worse than admitting the question cannot be answered, so needs_login() is true only for a confirmed logout. A host gating on it never nags about an agent that simply cannot be asked. Where a credential env var is set, that is reported as context without claiming the token is valid, since we have not checked it.

A real bug found on the way

Reading Copilot's login --help to write this turned up that COPILOT_GITHUB_TOKEN is its highest-precedence credential variable and was missing from essential_env. A host authenticating that way would have failed to authenticate at all once EnvPolicy::Minimal became the default in this release. Fixed here, ahead of publishing.

Testing

Parsing is split from spawning, so each agent's real output is unit-tested without needing its CLI installed. The live check runs by default alongside the version probe, since asking costs no quota, and fails loudly if a CLI changes its wording rather than letting the crate quietly report a working login as unknown.

107 unit tests, clippy clean, cargo package verifies.

Worth noting for release sequencing: #8 was merged while this was in flight, so 0.2.0 is already on master. This adds to it, and AuthStatus plus the COPILOT_GITHUB_TOKEN fix are both worth having in 0.2.0 rather than in a follow-up, since the token gap is a regression introduced by that release's own default change.