feat(site): marketing landing page for Mac + ScarfGo

Replace the gh-pages root placeholder with a real landing page that
sells both apps. Sources live at site/landing/ and publish through a
new scripts/site.sh that mirrors scripts/catalog.sh and scripts/wiki.sh
(check / build / preview / serve / publish, two-pass secret-scan, only
touches root files + assets/ on gh-pages so appcast.xml and templates/
stay disjoint).

Page is rust-palette tokens mapped from ScarfDesign, semantic HTML,
SEO + AEO infra (OpenGraph, Twitter cards, JSON-LD SoftwareApplication
+ MobileApplication + FAQPage, llms.txt, sitemap, manifest), 12-entry
FAQ, light/dark via prefers-color-scheme + manual toggle that swaps
both site chrome and screenshot variants. tools/og-image.html renders
the 1200x630 OG / 1200x600 Twitter cards via headless Chromium.

Real captures from the live Mac app (9 surfaces x light + dark) +
existing ScarfGo screenshots round out the imagery.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

site/landing/manifest.webmanifest

@@ -0,0 +1,24 @@
+{
+  "name": "Scarf",
+  "short_name": "Scarf",
+  "description": "Native macOS and iOS GUI for the Hermes AI agent.",
+  "start_url": "./",
+  "scope": "./",
+  "display": "browser",
+  "background_color": "#FAF7F2",
+  "theme_color": "#C2563D",
+  "icons": [
+    {
+      "src": "assets/icon-192.png",
+      "type": "image/png",
+      "sizes": "192x192",
+      "purpose": "any"
+    },
+    {
+      "src": "assets/icon-512.png",
+      "type": "image/png",
+      "sizes": "512x512",
+      "purpose": "any"
+    }
+  ]
+}