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>

src/core/graph/nodes/index.ts

@@ -68,8 +68,8 @@ import { GetVariable } from './variable/GetVariable';
 import { SetVariable } from './variable/SetVariable';
 
 /**
- * The built-in node set, one definition per file. Importing this module registers them;
- * the palette sorts by category and label, so the order here is documentation only.
+ * Importing this module registers the built-in nodes. The palette sorts by category and label, so
+ * the order here is documentation only.
  */
 export const BUILT_IN_NODES: readonly NodeDef[] = [
   // events