7f37a36722
Repos can pin a free-text notice (e.g. 'this repo is in maintenance mode',
or 'reviewers: focus on the public API only for this quarter') in
.pr-review.json:static_message. The string is stripped and capped at 400
chars (mirror of the existing instructions cap), then rendered as a
Markdown blockquote (> {msg}) directly under the REVIEW_HEADER so it
surfaces on every review without scrolling.
Plumbing: parse_repo_config exposes 'static_message'; format_review_body
accepts a static_message kwarg and inserts the blockquote before the
'### Summary of Changes' section; review_pr threads
config.get('static_message') to both call sites (salvage path + happy
path). Empty / non-string values are silently dropped, mirroring the
parser's 'ignore blank' handling for every other text field.