feat(standalone): demo follow-ups — waitlist, analytics, move-to-local, file tree, load progress

- Waitlist signup form on the home page (between Projects and Tools),
  cross-posting to the landing site's /api/waitlist (CORS + OPTIONS added there,
  gated by WAITLIST_ALLOWED_ORIGINS).
- Version badge gains a pcbjam.com landing-page link (VITE_LANDING_URL).
- Optional Plausible analytics from VITE_PLAUSIBLE_DOMAIN (off by default);
  wired into build-demo + both deploy workflows via vars.PLAUSIBLE_DOMAIN.
- Opening a read-only gallery project auto-"moves to local": it forks into a
  writable browser-local project at the same slug, shadowing the gallery row.
- Project + local-folder views use the same iconed tool launcher (ToolGrid)
  and a navigable directory FileTree instead of a flat file list.
- Boot overlay shows real wasm download progress (Module.instantiateWasm +
  streaming byte counter) and a "taking too long" state after 60s.
- Home Libraries section lists the active libs source (the read-only R2/CDN
  set in the demo) with a name filter; useLibs now reads libsSourceConfig.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TPJYx4urFVhdMjEmYfMCMD

site/astro.config.mjs

@@ -42,6 +42,15 @@ export default defineConfig({
         optional: true,
         default: 'PCBJam <hello@pcbjam.com>',
       }),
+      // Comma-separated origins allowed to cross-post the waitlist form (e.g. the
+      // static demo at demo.pcbjam.com, which has no backend of its own). Not a
+      // secret — just config. Same-origin submits never hit this.
+      WAITLIST_ALLOWED_ORIGINS: envField.string({
+        context: 'server',
+        access: 'public',
+        optional: true,
+        default: 'https://demo.pcbjam.com',
+      }),
     },
   },
 });