Official Rules, one markdown file per promotion

Name the file after the promotion slug: necann-nj-26.md renders at /promotions/necann-nj-26/rules.

These are compiled into the site at build time by scripts/build-promotion-rules.mjs, so publishing or amending a show's rules is a normal PR: reviewable, diffable, and attributable. That is deliberate. Rules are the legal spine of a promotion and should not be editable without a trace.

A promotion with no file here renders "The Official Rules are not published yet" and cannot accept entries. Nothing ever falls back to another promotion's rules.

Supported markdown: headings, paragraphs, ordered and unordered lists, bold, italics, links, horizontal rules. Anything else is emitted as plain escaped text rather than guessed at.

Two things gate a rules page going live:

1. 1This file exists for the slug.
2. 2`rules_published_at` is set on the promotion row in Supabase.

Both must be true. Until then the page says the rules are in review, which is the honest state while counsel still has them.