Follow Halon from the channel as a live checklist

Anyone in the channel can now follow an investigation without opening anything. See Following it in Slack.

A live checklist. The run's first message, such as Investigating INC-42, lists what Halon has looked at so far, such as Checked recent deploys and Read the code, each marked waiting, working, done or failed. It updates in place and says Investigated INC-42 once Halon is done.

A short answer in the channel. The answer goes to the channel in a few plain lines, what kind of answer it is and how sure Halon is, what is wrong in one sentence, up to three facts behind it and the suggested fix, with Apply fix and Open in Firefight. The full answer follows in the thread.

Fixes Firefight runs itself. A fix step that any of Firefight's own tools can do, such as inviting someone to the channel, assigning a role, paging or posting an update, now runs through Firefight as whoever applied the fix, so it is never left to you. A step whose change is already in place is marked done and says why, and each step that went through shows what it produced with its link, such as Opened a pull request: PR #856.

One message per fix. Applying a fix posts a single checklist, such as Fix for INC-003, that updates as each step moves and ends with Fix applied or Fix stopped. A step that fails says why in plain words and offers Try again. The fix also shows on the incident's timeline, with who applied it and each step's result.