Bypass the issue-link requirement for external contributors who have
earned the `trusted-contributor` tier label (>=5 merged PRs). Previously
only PRs with the `internal` label skipped the gate, meaning repeat
contributors still had to link an approved issue on every PR. Also
includes minor template and linting tweaks for contributor experience.
## Changes
- Add `trusted-contributor` bypass to the `check-issue-link` job
condition in `require_issue_link.yml`, with a secondary live-label API
fetch inside the script to cover the race where the `external` labeled
event payload doesn't yet include the tier label
- Add a `bypass-trusted-contributor` job in `require_issue_link.yml`
that removes `missing-issue-link` and reopens the PR when the
`trusted-contributor` label arrives after enforcement has already closed
it
- Reorder steps in `tag-external-contributions.yml` so the tier label is
applied *before* the `external` label — eliminates the race window
entirely since `trusted-contributor` is already on the PR when the
downstream `labeled` event fires
- Switch the tier-label step from `GITHUB_TOKEN` to the app token so the
`trusted-contributor` labeled event propagates to downstream workflows
- Add `hotfix` to allowed PR title types in `pr_lint.yml`
- Promote the English language policy to a blockquote callout in issue
and PR templates; add a "do not begin work without assignment" note to
the feature request template
