Repository bots as GitHub Actions

Description

Build and review repository bots that run as GitHub Actions and are triggered by workflows - triage and labelling bots, welcome and reminder comments, slash-command bots on issue and PR comments, release and changelog bots, scheduled housekeeping - with a GitHub App identity (actions/create-github-app-token), least-privilege tokens, safe handling of untrusted comment text, authorization checks for commands, loop prevention, idempotent comments, rate limits, and secrets and variables setup with a security analysis. Use whenever the user wants a bot, auto-labeler, auto-responder, slash commands like /deploy or /label, a bot that commits or opens PRs, "make the bot comment on PRs", or reviews bot workflows - even if they only say "automate our issue triage".