fix: backfill runs triage inline instead of label-toggle

GitHub does not fire new workflow runs when GITHUB_TOKEN creates label
events (built-in loop prevention). Replace the label-toggle backfill
approach with an inline version that mirrors the deterministic
reconciliation logic from issue-ai-maintenance directly: type labels,
command/distro labels, game/engine labels, Issue Type GraphQL sync,
and tmux false-positive cleanup. No AI call is made during backfill.

Also removes the now-unnecessary BACKFILL_TRIGGER_LABEL exemption from
the bot-loop guard in issue-ai-maintenance.

Author: dgibbs64