fix: hero demo popup closes on any outside click, add close button

Outside-click handling was scoped to the demo scene, so clicks elsewhere
on the page left the popup open and it felt unclosable. A document-level
listener now collapses it from anywhere, like a real extension popup,
and the popup header gained an explicit close button next to the version
link (hidden in the static mobile mockup).

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

website/template.html

@@ -444,6 +444,9 @@
                             <svg viewBox="0 0 16 16" fill="currentColor" style="width: 12px; height: 12px; display: block;"><path d="M8 0C3.58 0 0 3.58 0 8c0 3.54 2.29 6.53 5.47 7.59.4.07.55-.17.55-.38 0-.19-.01-.82-.01-1.49-2.01.37-2.53-.49-2.69-.94-.09-.23-.48-.94-.82-1.13-.28-.15-.68-.52-.01-.53.63-.01 1.08.58 1.23.82.72 1.21 1.87.87 2.33.66.07-.52.28-.87.51-1.07-1.78-.2-3.64-.89-3.64-3.95 0-.87.31-1.59.82-2.15-.08-.2-.36-1.02.08-2.12 0 0 .67-.21 2.2.82.64-.18 1.32-.27 2-.27.68 0 1.36.09 2 .27 1.53-1.04 2.2-.82 2.2-.82.44 1.1.16 1.92.08 2.12.51.56.82 1.27.82 2.15 0 3.07-1.87 3.75-3.65 3.95.29.25.54.73.54 1.48 0 1.07-.01 1.93-.01 2.2 0 .21.15.46.55.38A8.013 8.013 0 0016 8c0-4.42-3.58-8-8-8z"/></svg>
                             <span class="mockup-version">{{VERSION}}</span>
                         </a>
+                        <button class="mock-close-btn" id="demo-popup-close" type="button" aria-label="Close popup" title="Close popup">
+                            <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round" width="13" height="13" aria-hidden="true"><line x1="18" y1="6" x2="6" y2="18"/><line x1="6" y1="6" x2="18" y2="18"/></svg>
+                        </button>
                     </div>
                     <div class="mock-tabs">
                         <button class="mock-tab active" data-target="mock-room" title="Room settings and connection">Room</button>