Boost page navigation with htmx

Links and GET forms to wiki pages swap the next page into .shell instead
of loading a new document: the server answers boosted requests and
history restores with a partial (title, page actions out-of-band, shell
content). The header stays, browsers without cross-document view
transitions (Firefox) no longer flash between pages, and the swap runs
as a same-document view transition. Files, the editor, internal
endpoints and POST forms still navigate normally.

Back/Forward refetch pages (no snapshots that could predate a move or
delete); the tree rail keeps its scroll position and the content column
returns to where it was. Mutation redirects swap their result in the
same way. Page scripts that assumed a fresh document now also run after
a swap (toc, contents, companion, scroll-sync, search actions) or
register once (fitness).

The e2e suite now also runs in Firefox.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

assets/scroll-sync.js

@@ -45,17 +45,22 @@
     }
 
     // Reading mode: keep the latest scroll fraction recorded (throttled to one
-    // write per frame) so it is ready the moment the editor opens.
+    // write per frame) so it is ready the moment the editor opens. Boosted
+    // navigation replaces .center and changes the page without a reload, so
+    // listen on document and resolve both when writing.
     var pending = false;
-    center.addEventListener('scroll', function () {
-        if (pending) return;
+    document.addEventListener('scroll', function (e) {
+        if (pending || !e.target.classList || !e.target.classList.contains('center')) return;
         pending = true;
         requestAnimationFrame(function () {
             pending = false;
+            center = document.querySelector('.center');
+            if (!center) return;
             var m = maxScroll();
             try {
-                sessionStorage.setItem(key, JSON.stringify({ f: m > 0 ? center.scrollTop / m : 0, t: Date.now() }));
+                sessionStorage.setItem('scrollsync:' + location.pathname,
+                    JSON.stringify({ f: m > 0 ? center.scrollTop / m : 0, t: Date.now() }));
             } catch (e) {}
         });
-    }, { passive: true });
+    }, { capture: true, passive: true });
 })();