Document the GitHub release body convention

CHANGELOG.md

@@ -4,6 +4,8 @@ All notable public Spark changes should be recorded here.
 
 Spark follows human-readable release notes rather than a package-manager version contract. The release version is stored in `manifest.json` and mirrored in [README.md](README.md) and `CLAUDE.md`. When releasing, update all three version markers, add a dated changelog section, and publish a Git tag or GitHub release when the repo is ready for external consumers to pin versions.
 
+The GitHub release body is a summary, not a copy of the changelog section. Write one sentence framing the release, then a `### Highlights` list of at most five bullets, then a link to `CHANGELOG.md` at the release tag for the full record. A changelog entry stays as long as the change needs it to be, but the release page is scanned rather than read, so pasting a long entry into it produces notes nobody can follow. That is what happened to 1.3.0 and 1.4.0, both since rewritten. Use the 1.2.0 release as the reference format.
+
 ## 1.4.0 - 2026-09-08
 
 - Theme Settings > Style gained nine token-shaped settings: Layout holds `body_bg_color`, `border_color`, `radius_control`, `radius_card`, `section_padding`, `content_gap` and `container_max_width`; Type Scale holds `heading_scale` and `body_size`. `layouts/base.html` bridges them into `:root` with the same guarded pattern the font and colour settings use (noun-first properties such as `--control-radius` and `--section-padding-y`), and `css/input.css` registers namespace-first `@theme` keys that read them with today's values as fallbacks (`--radius-control: var(--control-radius, 4px)`); the names differ on purpose, because a key that reads a property of its own name is a self-reference and the bridge disconnects. The default option of `section_padding`, `content_gap`, `heading_scale` and `body_size` emits nothing. Component rules now read the bridge directly: body background and font-size, `.btn` radius, `.btn-secondary` and `.product-card-bordered` border colour, `.container` max-width, `.product-card` radius (with `overflow: hidden` so a rounded card clips its image), and the `.product-grid` / `.category-grid` gaps. In the six homepage sections the live branches swap design-decision literals for token utilities: `py-section-y md:py-section-y-md` on the four standard sections and `py-band-y md:py-band-y-md` on the promo band, `gap-content-md md:gap-content-lg` on the featured product columns, `text-display md:text-display-md` on the hero heading, `text-h1 md:text-h1-md` / `text-h2` / `text-h3` on the section headings, promo heading and featured product title, and `rounded-card` on the featured image and category tiles. Every `--text-*` key carries Tailwind's own line-height ratio, so the swap changes neither size nor leading. Placeholder and empty-state chrome stays literal because it signals missing configuration rather than the merchant-facing design language. A fixture render of the homepage before and after, at default settings, shows 0 computed-style differences and 0 differing pixels at 1280 and 375, for both a populated homepage and a fresh store rendering only `settings_data.json`. `tests/test_style_tokens.py` pins the fallbacks, the bridge conditions, the live-versus-placeholder split and the nine setting ids. `assets/main.css` grew from 48219 to 50298 bytes (#56).