backport/<branch> commit status is never updated after the backport lands

[mengw15]

What happened?

direct-backport-push.yml writes a backport/<target> commit status onto the squash commit on main, then nothing ever updates it — not when the backport PR merges, not when it is closed. The status records which code path ran at merge time, not whether the fix reached the branch, which is what it reads as.

Six landed backports still carry a red status on main today:

source	backport	landed	status on main now
#8562	#8585	v1.2, 09-19	failure — "Draft backport PR #8585 opened"
#7348	#7530	v1.2, 08-13	failure — "Draft backport PR #7494 opened"
#7347	#7529	v1.2, 08-13	failure — "Draft backport PR #7495 opened"
#7327	#7518	v1.2, 08-13	failure — "Draft backport PR #7401 opened"
#7234	#7306	v1.2, 08-04	failure — "Draft backport PR #7291 opened"
#8498	#8500	v1.3, 09-11	failure — "Backport failed"

The four middle rows also name a PR that was closed without merging — the one the first attempt opened — so the link goes to a dead PR.

How to reproduce?

1. Merge a fix: PR whose backport conflicts, so a draft backport PR opens.
2. Finish and merge that backport PR.
3. GET /repos/apache/texera/commits/<the source squash sha>/status — backport/<target> is still failure.

Fix: a handler on the backport PR closing that resolves the source commit's status — success when merged, failure when closed unmerged. It belongs with the removal of the unreachable push-backports job, which holds the only success write for this context.

Version/Branch

main