feat: browser-aware CTAs, tidier hero demo, comparison guides link

- Hero CTAs: the install buttons are compact (just the browser name) so all
  three fit one line; JS detects the visitor's browser and expands that one
  to the full "Add to X" call to action. Unknown browsers stay compact.
- Hero demo: caption now sits directly under the two windows (absolutely
  positioned to the card cascade) instead of far below the tall scene. The
  scene keeps a fixed height that already fits the open popup, so the
  vertically centered hero never jumps when the popup toggles.
- The background window now also shows a (non-interactive) extension icon,
  making it clear both browsers have KoalaSync installed.
- Escape now also closes the demo popup.
- Added a link from the comparison table to the fuller alternatives/guides
  hub, localized in all 15 languages.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

website/app.js

@@ -78,6 +78,23 @@ document.addEventListener('DOMContentLoaded', () => {
         });
     }
 
+    // Highlight the CTA for the visitor's browser: it expands to the full
+    // "Add to X" label while the others stay compact. Unknown browsers keep
+    // all three compact.
+    try {
+        const ua = navigator.userAgent;
+        let detected = null;
+        if (/Firefox\//.test(ua) && !/Seamonkey\//.test(ua)) {
+            detected = 'firefox';
+        } else if (/Chrome\//.test(ua) || /Chromium\//.test(ua) || /Edg\//.test(ua) || /OPR\//.test(ua)) {
+            detected = 'chrome';
+        }
+        if (detected) {
+            const btn = document.querySelector('.btn-install[data-browser="' + detected + '"]');
+            if (btn) btn.classList.add('is-detected');
+        }
+    } catch (_) { /* leave all buttons compact */ }
+
     // Open collapsed section blocks when the URL directly targets them
     const hashCollapseMap = { '#faq': 'faq-collapse', '#self-hosting': 'selfhost-collapse' };
     const collapseId = hashCollapseMap[window.location.hash];
@@ -809,6 +826,15 @@ document.addEventListener('DOMContentLoaded', () => {
             });
         }
 
+        // Escape closes the popup as well
+        document.addEventListener('keydown', (e) => {
+            if (e.key !== 'Escape') return;
+            if (!scene.classList.contains('popup-open')) return;
+            userTookOver = true;
+            finishDemo();
+            setPopupOpen(false);
+        });
+
         const runDemo = async () => {
             if (demoStarted || userTookOver || reduceMotion) return;
             demoStarted = true;