Trim needless comments and fix the picker width

Remove comments that only restate the code, keeping the section banners
and the notes that carry a reason, a measured fact or an external
contract.

ButtonOptions.width claimed to be a fixed width but only set minWidth,
so the Graph and Texture pickers grew with the name they showed. It is
now what it promises, with a separate minWidth for the buttons that have
two forms. Narrow buttons shrink their padding, otherwise a 24px icon
button had 8px left for its glyph and truncate dropped it entirely.

__gm.labelsDropped() guards that class: the overflow guard only saw text
that was too wide, never a label truncated to nothing.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/ui/math.test.ts

@@ -52,8 +52,7 @@ describe('formatNumber', () => {
   });
 
   it('shows a field of integral values without a decimal point at all', () => {
-    // What `NumberFieldOptions.decimals: 0` buys: a pixel index or a count of tiles reads
-    // "33" and "4" instead of "33.000" and "4.000".
+    // What `NumberFieldOptions.decimals: 0` buys: a pixel index reads "33", not "33.000".
     expect(formatNumber(33, 0)).toBe('33');
     expect(formatNumber(-4, 0)).toBe('-4');
     // The minus-zero rule holds at every precision, not just the default one.