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/css/custom.css

@@ -10,10 +10,15 @@
 .prompt {
   font-family: var(--font-family-mono);
   display: flex;
-  flex-wrap: wrap;
+  /* stay on ONE line: when the command gets too wide, clip the left (older)
+     part terminal-style and keep the caret/right end visible (shell.js scrolls
+     it to the end). previously flex-wrap:wrap dropped to a 2nd line and bugged. */
+  flex-wrap: nowrap;
   align-items: flex-start;
   gap: 0;
   line-height: 1.5;
+  overflow: hidden;
+  white-space: nowrap;
 }
 .prompt__user { font-weight: 700; }
 .prompt__path { color: var(--color-text-muted); }
@@ -299,9 +304,11 @@ body {
   user-select: text;
 }
 
-/* dotted content + footer links: unchanged at rest, invert to black on hover */
+/* dotted content + footer links: unchanged at rest, invert to black on hover.
+   include the header language switch so en/de behave like every other link. */
 main a:hover,
-footer a:hover {
+footer a:hover,
+.lang-switch:hover {
   background: var(--color-text-primary);
   color: var(--color-bg-primary);
   border-bottom-color: transparent;