* ci: replace actions/stale with bot-aware mark-stale script
actions/stale uses updatedAt to measure inactivity, so any bot event
(e.g. the /remove-reviewer acknowledgment comment) resets the stale
countdown even when there has been no meaningful human activity for
months. PR #6332 was last touched by a human on 2026-04-02 but was
not flagged because a reviewer-removal on 2026-06-11 refreshed the
timestamp.
Replace the actions/stale step with a custom mark-stale.js script
(same pattern as alert-stale.js) that only counts non-bot comments,
non-bot review submissions, and commits as meaningful activity. The
script also removes the stale label if such activity occurs after the
label was applied.
* ci: fix draft-stale keepalive for external contributors
Two bugs with the keepalive checkbox on draft-stale PRs:
1. External contributors (fork authors) lack write access to edit the
bot's comment, so clicking the checkbox silently fails for them.
Fix: also treat a new non-bot comment posted after the keepalive
comment as a sufficient keepalive signal.
2. The stale label could take up to 24 hours to be removed (daily cron
only). Fix: add an issue_comment.created trigger so draft-pr-policy
fires immediately when someone comments on a stale draft PR.
mark-stale and alert-stale are guarded to only run on
schedule/workflow_dispatch, not on every comment.
Also fix lastRealActivityAt to exclude bot comments (matching
mark-stale.js), so the keepalive and "Thanks for confirming" bot
comments don't count as real activity when measuring staleness.
