Add Starlight documentation site (32 pages, 9 sidebar groups)

Astro 5 + Starlight 0.37 site at site/ with teal/steel theme.
Content sourced from 14 reverse engineering docs, master reference,
and custom firmware source. Includes Tabs, Badge, Steps, Aside,
FileTree, and CardGrid components throughout. DiSEqC SVGs with
click-to-zoom via starlight-image-zoom. All internal links validated.
Pagefind search indexes all 32 pages.

site/src/content.config.ts

@@ -0,0 +1,6 @@
+import { defineCollection } from 'astro:content';
+import { docsSchema } from '@astrojs/starlight/schema';
+
+export const collections = {
+  docs: defineCollection({ schema: docsSchema() }),
+};