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/model/Properties.ts

@@ -1,32 +1,26 @@
 /** Colors are stored as 0xRRGGBB numbers. */
 export type PropertyValue = number | string | boolean;
 
-/** Sparse map of property key → value (asset properties or scene-object overrides). */
 export type PropertyBag = Record<string, PropertyValue>;
 
-/** Writes `value` into the bag, or removes the key when the value is undefined (an undo of "no value"). */
+/** `undefined` removes the key, which is how an undo of "no value" works. */
 export function setBagValue(bag: PropertyBag, key: string, value: PropertyValue | undefined): void {
   if (value === undefined) delete bag[key];
   else bag[key] = value;
 }
 
-/** A point in world or screen space. */
 export interface Vec2 {
   x: number;
   y: number;
 }
 
-/**
- * Where a scene object sits: `x`/`y` in world units, `z` is the draw order. Higher `z` is
- * drawn on top; objects with equal `z` keep their hierarchy order.
- */
+/** `x`/`y` in world units; `z` is the draw order – higher is on top, ties keep hierarchy order. */
 export interface Position extends Vec2 {
   z: number;
 }
 
 export type Axis = keyof Position;
 
-/** A full position from a 2D point (`z` = 0) or a position (copied). */
 export function toPosition(point: Vec2 | Position): Position {
   return { x: point.x, y: point.y, z: 'z' in point ? point.z : 0 };
 }