fix: filebrowser scroll+lang hover+black-flash+shell one-line

- filebrowser: select() only scrollIntoView on keyboard, not hover
- lang-switch: .lang-switch:hover → invert rule (header excluded before)
- black-flash: color-scheme light; dark script sets colorScheme
- shell: flex-wrap nowrap; keepEnd() scrolls on input

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

assets/js/filebrowser.js

@@ -31,7 +31,7 @@
     if (img.complete) img.style.opacity = "1";   // already cached → no fade
   }
 
-  function select(i, silent) {
+  function select(i, silent, scroll) {
     if (!rows.length) return;
     if (i < 0) i = 0;
     if (i >= rows.length) i = rows.length - 1;
@@ -39,7 +39,9 @@
     for (var r = 0; r < rows.length; r++) rows[r].classList.remove("is-selected");
     var a = rows[i];
     a.classList.add("is-selected");
-    if (a.scrollIntoView) a.scrollIntoView({ block: "nearest" });
+    // only scroll for keyboard nav — scrolling on hover nudges edge rows out from
+    // under the cursor, so the top/bottom row "sometimes" can't be clicked.
+    if (scroll && a.scrollIntoView) a.scrollIntoView({ block: "nearest" });
 
     var src = a.getAttribute("data-img");
     var tkey = a.getAttribute("data-text");
@@ -100,8 +102,8 @@
     var t = e.target;
     if (t && (t.isContentEditable || /^(input|textarea|select)$/i.test(t.tagName))) return;
     if (!rows.length) return;
-    if (e.key === "ArrowDown") { e.preventDefault(); select(cur + 1); }
-    else if (e.key === "ArrowUp") { e.preventDefault(); select(cur - 1); }
+    if (e.key === "ArrowDown") { e.preventDefault(); select(cur + 1, false, true); }
+    else if (e.key === "ArrowUp") { e.preventDefault(); select(cur - 1, false, true); }
     else if (e.key === "Enter") {
       var href = rows[cur] && rows[cur].getAttribute("href");
       if (href) { if (window.pjax) window.pjax(href); else window.location.href = href; }