Flip Elsewhen between Fahrenheit and Celsius with Alt+T (#13450)

* Flip Elsewhen between Fahrenheit and Celsius with Shift+T

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

* Flip Elsewhen's temperature units with Alt+T instead of Shift+T

PanelKeyCatcher's textKey now carries the held modifiers, which is how the
panel tells Alt+T from T. Existing handlers take only the text and are
unaffected.

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

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

shell/Ui/PanelKeyCatcher.qml

@@ -14,7 +14,7 @@ import QtQuick
 //       onActivateRequested: root.activateCursor()
 //       onCloseRequested: root.close()
 //       onDeleteRequested: root.deleteSelected()
-//       onTextKey: function(t) { if (t === "r") root.refresh() }
+//       onTextKey: function(t, modifiers) { if (t === "r") root.refresh() }
 //
 //       Column { ... panel content ... }
 //     }
@@ -41,7 +41,8 @@ Item {
   signal closeRequested()
   signal deleteRequested()
   signal tabRequested(int direction)
-  signal textKey(string text)
+  // The held modifiers ride along, so a panel can tell Alt+T from T.
+  signal textKey(string text, int modifiers)
 
   focus: true
   Keys.priority: Keys.BeforeItem
@@ -79,7 +80,7 @@ Item {
       deleteRequested(); event.accepted = true; return
     }
     if (event.text && event.text.length === 1) {
-      textKey(event.text)
+      textKey(event.text, event.modifiers)
     }
   }
 }