Add larger gap between function row and number row (~half unit)

Matches physical 104-key keyboard proportions where the F-key row
sits separated from the main key area.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: asimone

src/keyboardLayout.js

@@ -5,17 +5,18 @@
 
 const U = 44; // unit
 const G = 4;  // gap
+const FROW_GAP = 20; // extra space between function row and number row
 
 export const KEYBOARD_WIDTH  = 1040;
-export const KEYBOARD_HEIGHT = 268;
+export const KEYBOARD_HEIGHT = 288;
 
 function key(id, label, col, row, w = 1, h = 1, altLabel) {
   return {
     id,
     label,
     altLabel,
     x: col * U + G,
-    y: row * U + G,
+    y: row * U + G + (row >= 1 ? FROW_GAP : 0),
     w: w * U - G,
     h: h * U - G,
   };