README gate confirmation command can be used by any commenter, bypassing the "readme: pending" gate

Description

The handle-confirmation job in .github/workflows/readme-pr-check.yml
(line 63) swaps the gating label from readme: pending to
readme: ready for review whenever any comment on the PR contains the magic
string, without checking who wrote the comment:

handle-confirmation:
  if: github.event_name == 'issue_comment' && github.event.issue.pull_request && contains(github.event.comment.body, '/i-promise-this-is-not-a-new-server')

The job verifies neither github.event.comment.user.login /
author_association, nor that the commenter is the PR author or a maintainer.
The gate exists to enforce the policy "we are no longer accepting PRs to add
new servers to the README" (see the bot's comment posted by
check-readme-only). Any third party — not just the PR author — can comment
/i-promise-this-is-not-a-new-server and move the PR past the gate, since the
magic string is written out verbatim in the bot's own public comment.

Trigger scenario

1. A fork PR modifies only README.md (e.g. to add a new server), so
   check-readme-only applies the readme: pending label.
2. The PR author — or any unrelated user — comments
   /i-promise-this-is-not-a-new-server.
3. handle-confirmation removes readme: pending and adds
   readme: ready for review, silently bypassing the maintainers' gate.

Impact

A review-process bypass: new-server PRs that the maintainers intended to block
can be marked ready for review without maintainer involvement. No secrets or
OIDC capabilities are exposed (the job only has pull-requests: write), so
the impact is limited to workflow integrity.

Suggested fix

Restrict the confirmation to trusted actors, e.g.:

if: github.event_name == 'issue_comment' && github.event.issue.pull_request && contains(github.event.comment.body, '/i-promise-this-is-not-a-new-server') && contains(fromJSON('["OWNER","MEMBER","COLLABORATOR"]'), github.event.comment.author_association)

(or require the commenter to equal github.event.issue.user.login, if the
intent is that only the PR author may confirm).

I'd be happy to open a PR with the author_association check. Thanks!

Open .github/workflows/readme-pr-check.yml and inspect the handle-confirmation job around line 63, including the issue_comment trigger and author fields described in the report. Restrict the confirmation to the intended trusted actor and verify that an unrelated commenter can no longer change the labels while the intended confirmation still moves readme: pending to readme: ready for review.