Fix preset-grid orphan row for 5/6-item preset sets

PresetButtonGrid rendered every preset set into a fixed 4-column
.preset-grid, so 5-item sets (RADIUS_PRESETS, SPACING_PRESETS,
IMAGE_RADIUS_PRESETS, FONT_WEIGHTS, NavStylePanel's GAP_PRESETS)
wrapped a single lone button onto its own row, and the 6-item
TEXT_SIZES split unevenly (4+2).

PresetButtonGrid now derives a column count from presets.length via
defaultPresetGridColumns() -- 5-item sets get a single row of 5,
6-item sets split into two even rows of 3, and anything else keeps
the classic 4-column grid -- with an optional `columns` prop for
explicit overrides. This fixes every existing call site automatically
rather than threading an explicit count through each one.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

craft/src/panels/right/styles/PresetButtonGrid.columns.test.ts

@@ -0,0 +1,38 @@
+import { describe, it, expect } from 'vitest';
+import { defaultPresetGridColumns } from './shared';
+import { RADIUS_PRESETS, SPACING_PRESETS, IMAGE_RADIUS_PRESETS, FONT_WEIGHTS, TEXT_SIZES, FONT_FAMILIES } from '../../../constants/presets';
+
+/*
+ * Regression: 5-item preset sets (RADIUS_PRESETS, SPACING_PRESETS,
+ * IMAGE_RADIUS_PRESETS, FONT_WEIGHTS, and NavStylePanel's ad-hoc
+ * GAP_PRESETS) left a lone orphan button on its own row under the old
+ * fixed 4-column .preset-grid. PresetButtonGrid now derives a column
+ * count from the preset length instead.
+ */
+describe('defaultPresetGridColumns', () => {
+  it('gives 5-item sets their own single row (no orphan)', () => {
+    expect(defaultPresetGridColumns(RADIUS_PRESETS.length)).toBe(5);
+    expect(defaultPresetGridColumns(SPACING_PRESETS.length)).toBe(5);
+    expect(defaultPresetGridColumns(IMAGE_RADIUS_PRESETS.length)).toBe(5);
+    expect(defaultPresetGridColumns(FONT_WEIGHTS.length)).toBe(5);
+    expect(defaultPresetGridColumns(5)).toBe(5); // NavStylePanel's GAP_PRESETS
+  });
+
+  it('splits 6-item sets into two even rows of 3 (was 4+2 uneven)', () => {
+    expect(defaultPresetGridColumns(TEXT_SIZES.length)).toBe(3);
+  });
+
+  it('keeps the classic 4-column grid for sets that already divide evenly', () => {
+    expect(defaultPresetGridColumns(FONT_FAMILIES.length)).toBe(4); // 8 items
+    expect(defaultPresetGridColumns(4)).toBe(4);
+    expect(defaultPresetGridColumns(3)).toBe(4);
+  });
+
+  it('never leaves a single orphan on the final row for any count 1-12', () => {
+    for (let n = 1; n <= 12; n++) {
+      const cols = defaultPresetGridColumns(n);
+      const isLoneOrphan = n > cols && n % cols === 1;
+      expect(isLoneOrphan).toBe(false);
+    }
+  });
+});

craft/src/panels/right/styles/shared.tsx

@@ -84,9 +84,30 @@ interface PresetButtonGridProps {
   presets: { label: string; value: string }[];
   activeValue: string | undefined;
   onSelect: (value: string) => void;
+  /** Explicit column count. When omitted, a column count is derived from
+   *  `presets.length` (see `defaultPresetGridColumns`) so odd-sized preset
+   *  sets (5, 6, ...) don't leave a lone orphan button dangling on its own
+   *  row under the fixed 4-column grid. */
+  columns?: number;
 }
-export const PresetButtonGrid: React.FC<PresetButtonGridProps> = ({ presets, activeValue, onSelect }) => (
-  <div className="preset-grid">
+
+/** Picks a column count that avoids a single orphan on the last row.
+ *  4-or-fewer presets keep the classic single row of 4. 5 gets its own
+ *  row (5 cols). 6 splits into two even rows of 3. Anything else falls
+ *  back to a 4- or 3-column grid depending on which divides evenly. */
+export function defaultPresetGridColumns(count: number): number {
+  if (count <= 4) return 4;
+  if (count === 5) return 5;
+  if (count === 6) return 3;
+  if (count % 4 === 0) return 4;
+  if (count % 3 === 0) return 3;
+  return 4;
+}
+
+export const PresetButtonGrid: React.FC<PresetButtonGridProps> = ({ presets, activeValue, onSelect, columns }) => {
+  const cols = columns ?? defaultPresetGridColumns(presets.length);
+  return (
+    <div className="preset-grid" style={{ gridTemplateColumns: `repeat(${cols}, 1fr)` }}>
       {presets.map((p) => (
         <button
           key={p.value}
@@ -97,7 +118,8 @@ export const PresetButtonGrid: React.FC<PresetButtonGridProps> = ({ presets, act
         </button>
       ))}
     </div>
-);
+  );
+};
 
 interface GradientSwatchGridProps {
   activeValue: string | undefined;