i18n: language picker in the bottom-right corner

Replaces the EN/ES/RU buttons in the Visual Presets dock with a picker
that scales to many languages: a globe button with the current code
next to the POWER UP chip, opening a list of languages named in their
own language with their codes, the current one first and checked. A
search field appears past 8 languages. Keyboard: arrows, Home/End,
Enter/Space, Esc, type-ahead; keys stay in the list while it is open.
Choosing a language still asks before dropping unsaved work, then
reloads. Phones get the globe alone and a full-width sheet; the layout
uses logical properties for right-to-left languages.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/ui/styles/provider-settings.css

@@ -4,11 +4,9 @@
    mono kickers. The chip retires once every key is configured.
    ============================================================ */
 
+/* The chip sits in the bottom-right corner row (#corner-actions,
+   locale-picker.css), which owns the position. */
 #key-setup-chip {
-  position: fixed;
-  right: 0.9rem;
-  bottom: 0.9rem;
-  z-index: 60;
   display: flex;
   align-items: center;
   gap: 0.4rem;
@@ -389,13 +387,6 @@ body.scene-playback-mode #key-setup {
   display: none;
 }
 
-@media (max-width: 620px) {
-  /* Clear the dock. Desktop-first app; this is a courtesy, not a layout. */
-  #key-setup-chip {
-    bottom: 5.8rem;
-  }
-}
-
 /* Provider Settings additions: externally-managed badge + per-row remove. */
 .key-setup-external {
   padding: 0.05rem 0.3rem;