feat: ✨ WebGL graphics blog post, Gerber demo on landing page, open-source license notices

- Blog: porting-kicad-graphics-to-webgl post + GAL native/WebGL comparison images and <GalCompare>
- Landing page: embed lazily-loaded Gerber demo section + footer "Live demo" link
- Licensing: /licenses page (GPLv3 + wxWindows/LGPL-v2 breakdown, ahilss credit, corresponding-source offer) and a footer build-SHA link
- Docs: CLAUDE.md + README note to bump the hardcoded footer BUILD_SHA on each release

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

README.md

@@ -170,6 +170,23 @@ See **[docs/README.md](docs/README.md)** for the full documentation map. Highlig
 - [Debugging Guide](docs/debugging/DEBUG.md) - Asyncify/WASM debugging
 - [Tests README](tests/README.md) - Test infrastructure
 
+## Landing page / website
+
+The marketing site and landing page live in [`site/`](site/) (Astro), deployed as
+static assets to Cloudflare R2.
+
+**On every release, bump the build SHA.** `site/src/components/Footer.astro` has a
+hardcoded `BUILD_SHA` constant that is shown in the footer and links to the
+corresponding commit. Because the main-repo commit pins the KiCad and wxWidgets
+submodule revisions implicitly, this is our GPLv3 **corresponding-source** pointer
+(surfaced on `/licenses`). The site is static, so nothing sets it automatically —
+update `BUILD_SHA` by hand to the deployed `pcbjam` commit each time you release.
+
 ## License
 
 KiCad is GPL-3.0. This project follows the same license.
+
+The site combines KiCad (GPLv3) with the wxWidgets fork; the wxWidgets WebAssembly
+port files are LGPL v2 (without the wxWindows binary exception). See the
+`/licenses` page (`site/src/content/legal/licenses.md`) for the full breakdown and
+the corresponding-source offer.