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>

src/layout/KeyGeometry.h

@@ -12,22 +12,25 @@ struct KeyboardMetrics {
 };
 
 // The keys on screen: blocks of rows, side by side.
-using Block = QList<Row>;
+struct Block {
+    QList<Row> rows;
+    bool fillHeight = false; // rows grow to span the full height instead of sharing the row height
+};
 
 // Lays out blocks to fill `size`. Returns one rect per key, block by block in
 // row order (spacers included). One key unit has the same width everywhere;
-// all rows share one height, and shorter blocks sit at the bottom. In each
-// block, stretch keys grow to make their row as wide as the widest one, and
-// remaining shorter rows are centered.
+// rows share one height, set by the tallest block that doesn't fill, and
+// shorter blocks sit at the bottom. In each block, stretch keys grow to make
+// their row as wide as the widest one, and remaining shorter rows are centered.
 QList<QRectF> computeKeyRects(const QList<Block> &blocks, QSizeF size, KeyboardMetrics metrics = {});
 inline QList<QRectF> computeKeyRects(const Layer &layer, QSizeF size, KeyboardMetrics metrics = {})
 {
-    return computeKeyRects({layer.rows}, size, metrics);
+    return computeKeyRects({{layer.rows}}, size, metrics);
 }
 
 // Total width of a row in key units, before stretching.
 qreal rowUnits(const Row &row);
 // Width of all blocks in key units, ignoring gaps.
 qreal totalUnits(const QList<Block> &blocks);
-// Rows of the tallest block.
+// Rows of the tallest block that sets the row height (see computeKeyRects).
 qsizetype totalRows(const QList<Block> &blocks);