One Run notification per Spec run #148

Parent

#139

What to build

A Spec run sends at most one Run notification, when it ends, under the same rules as a Run: --email [address], email.always, --no-email, with the notification preflight done once before any Ticket starts.

• Subject: [thirdshift] <owner>/<repo>#<spec> <Spec title>: <outcome>, the outcome being ready for review, merged, failed or interrupted.
• Body: what a Run's notification holds (the Spec PR URL if any, the failure cause if failed, hostname, duration), plus one line per Ticket with its outcome, as in the stderr summary.
• Ticket Runs never send a notification of their own, whatever the User config says.
• A failed send is a warning on stderr that never changes the Spec run's outcome or exit code.

The README says a Spec run sends one notification for the whole Spec.

Acceptance criteria

• A Spec run with --email that ends with a ready Spec PR sends exactly one notification, with outcome ready for review and a line per Ticket
• A Failed spec run with --email sends exactly one notification, with outcome failed and each Ticket's outcome
• With email.always = true, Ticket Runs send nothing and the Spec run sends one; --no-email sends none
• A missing address or RESEND_API_KEY stops the Spec run before any Ticket starts
• A Resend error leaves the Spec run's exit code and stdout unchanged, with a warning on stderr
• README documents notifications for Spec runs

Blocked by

• Going as far as it can: Failed spec runs #144