feat: build the site with Astro Starlight

generate_site.py writes the Starlight project in website/ and nothing
else: mkdocs.yml, the MkDocs hooks, theme overrides and stylesheet go,
and the wiki is written in Starlight's syntax. Both workflows set up
Node with the official actions/setup-node pinned by commit, run npm ci
from the committed lockfile, build with the strict link validator and
check the result with validate_site.py.

The search weighs a page by what it answers: Start here pages first,
a system page's cards and file names before a guide citing them, deep
guides, launchers, aliases and frozen copies after. Status badges,
hash blocks and the export change lists leave the index. The ranking
sits at the centre of a range where the 13 queries of search_gate.py
all answer, in the search box itself.

839 pages, every URL and 45,611 ids match the MkDocs build. The tests
read the Starlight content and syntax.

website/src/components/MarkdownContent.astro

@@ -1,14 +1,15 @@
 ---
-// Search ranking: Pagefind multiplies the score of words inside a weighted
-// element, so a Start here page outranks the reference page that names it.
+// Search weight: Pagefind multiplies the score of words inside a weighted
+// element, so a Start here page outranks the reference page that names it,
+// and an emulator outranks its launcher or its frozen copy.
 import Default from '@astrojs/starlight/components/MarkdownContent.astro';
 
-const { boost } = Astro.locals.starlightRoute.entry.data;
+const { searchWeight } = Astro.locals.starlightRoute.entry.data;
 ---
 
 {
-	boost ? (
-		<div data-pagefind-weight={String(Math.min(10, boost * 2))}>
+	searchWeight ? (
+		<div data-pagefind-weight={String(searchWeight)}>
 			<Default><slot /></Default>
 		</div>
 	) : (

website/src/content.config.ts

@@ -12,8 +12,8 @@ export const collections = {
 				// Who the page is written for, from someone who knows nothing
 				// (start) to someone adding to the project (contribute).
 				level: z.enum(['start', 'setup', 'explore', 'reference', 'contribute']).optional(),
-				// Search ranking of the first two levels.
-				boost: z.number().min(1).max(10).optional(),
+				// How much the site search weighs the page's words (1 by default).
+				searchWeight: z.number().min(0.1).max(10).optional(),
 				// The date the page's content carries, for the sitemap.
 				lastmod: z.string().optional(),
 			}),

website/src/styles/retrobios.css

@@ -367,7 +367,8 @@
 
 /* Collapsible blocks keep the callout colour of their role */
 .sl-markdown-content details.rb-details {
-	border-inline-start: 4px solid var(--sl-color-blue);
+	border: 1px solid var(--sl-color-blue);
+	border-radius: 4px;
 	background: var(--sl-color-blue-low);
 	padding: 0.6rem 1rem;
 }