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/core/holders.test.ts

@@ -1,7 +1,6 @@
 /**
- * Container assets hold placed objects just like scenes do. Anything that walks "all placed
- * objects" has to cover both – the tests here pin the places that used to look at scenes only.
- * The history tests pin that a rejected undo leaves the stacks usable.
+ * Container assets hold placed objects just like scenes do, so anything that walks "all placed
+ * objects" has to cover both. Plus: a rejected undo leaves the stacks usable.
  */
 import { describe, expect, it } from 'vitest';
 import { type Command, CommandError } from '../../src/core/commands/Command';
@@ -71,7 +70,6 @@ describe('RenameVariableCommand', () => {
   });
 });
 
-/** Applies a marker to the project; its undo refuses to run. */
 class RefusingUndo implements Command {
   readonly label = 'Refusing';
   execute(project: { name: string }): void {