Numeric keypad spans the full keyboard height

- Sections take "fillHeight": their rows stretch over the whole key area
  instead of sitting at the bottom at the shared row height
- Rows of other blocks are unaffected; the template turns it on for the numpad

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

layouts/template.json

@@ -66,6 +66,7 @@
         {
             "id": "numpad",
             "name": "Numeric keypad",
+            "fillHeight": true,
             "rows": [
                 ["7", "8", "9", "/", {"type": "backspace"}],
                 ["4", "5", "6", "*", "-"],