Give every behavior variable one row shape on asset and instance

buildStructBlock only covered structs, so a placed instance drew numbers,
text, bools and lists through createFieldRow on a 64 px name column while
its struct block sat on the asset's grid below it. variableRows.ts now
builds the row for every variable kind on both sides; the edit option
decides what the owner may change (asset: rename, x, item kind; instance:
revert and push). Label and Button take a fixed width so the mark column
no longer shifts names when a list shows its item-kind picker.

The two structFields calls that became dead with 9f48257 are gone. The
e2e steps locate the Enabled toggle through __gm.inspectorField instead
of clicking a fixed offset from its label.

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

src/ui/widgets/Button.ts

@@ -1,7 +1,7 @@
 import { type FederatedPointerEvent, Graphics, Text, CanvasTextMetrics } from 'pixi.js';
 import { drawControlBox } from '../draw';
 import { centreY } from '../math';
-import { Theme, textStyle } from '../Theme';
+import { Theme, textStyle, type TextStyleToken } from '../Theme';
 import { type Size, Widget } from '../Widget';
 import { truncate } from './Label';
 
@@ -12,6 +12,8 @@ export interface ButtonOptions {
   /** Floor only – for a button whose label changes between forms and must grow with them. */
   minWidth?: number;
   align?: 'center' | 'left';
+  /** Text style of the label when the button is not on an accent fill. */
+  style?: TextStyleToken;
   onClick?: () => void;
 }
 
@@ -26,6 +28,7 @@ export class Button extends Widget {
   variant: NonNullable<ButtonOptions['variant']>;
   protected readonly align: NonNullable<ButtonOptions['align']>;
   protected readonly fixedWidth: number;
+  private readonly style: TextStyleToken;
   onClick?: () => void;
 
   constructor(text: string, options: ButtonOptions = {}) {
@@ -39,7 +42,8 @@ export class Button extends Widget {
     this.fixedWidth = options.width ?? 0;
     this.minWidth = this.fixedWidth || (options.minWidth ?? 0);
     this.fullText = text;
-    this.labelText = new Text({ text, style: textStyle(this.variant === 'primary' ? 'accent' : 'body') });
+    this.style = options.style ?? 'body';
+    this.labelText = new Text({ text, style: textStyle(this.variant === 'primary' ? 'accent' : this.style) });
     this.addChild(this.bg, this.labelText);
 
     // Leaving while pressed cancels the click: a release elsewhere must not activate.
@@ -148,7 +152,7 @@ export class Button extends Widget {
       this.bg.roundRect(0.5, 0.5, this.w - 1, this.h - 1, Theme.radius).stroke({ width: 1, color: stroke });
     }
     // Style first: it decides the glyph widths that the truncation then measures against.
-    this.labelText.style = textStyle(this.onAccent ? 'accent' : 'body');
+    this.labelText.style = textStyle(this.onAccent ? 'accent' : this.style);
     const label = this.labelText;
     label.text = truncate(this.fullText, label.style, this.labelSlot());
     const x = this.align === 'left' ? Theme.padding : (this.w - label.width) / 2;

src/ui/widgets/Label.ts

@@ -7,6 +7,8 @@ export interface LabelOptions {
   style?: TextStyleToken;
   align?: 'left' | 'center' | 'right';
   padding?: number;
+  /** Fixed width – a column that must not grow with a long text; the text is truncated instead. */
+  width?: number;
 }
 
 /** Single-line text that truncates with an ellipsis when narrower than its content. */
@@ -15,6 +17,7 @@ export class Label extends Widget {
   private fullText: string;
   private readonly align: NonNullable<LabelOptions['align']>;
   private readonly padding: number;
+  private readonly fixedWidth: number;
 
   constructor(text = '', options: LabelOptions = {}) {
     super();
@@ -22,6 +25,8 @@ export class Label extends Widget {
     this.fullText = text;
     this.align = options.align ?? 'left';
     this.padding = options.padding ?? 0;
+    this.fixedWidth = options.width ?? 0;
+    this.minWidth = this.fixedWidth;
     this.textNode = new Text({ text, style: textStyle(options.style ?? 'body') });
     this.addChild(this.textNode);
     this.minHeight = Theme.rowHeight;
@@ -45,6 +50,7 @@ export class Label extends Widget {
   }
 
   override measure(): Size {
+    if (this.fixedWidth) return { w: this.fixedWidth, h: this.minHeight };
     const metrics = CanvasTextMetrics.measureText(this.fullText, this.textNode.style);
     return {
       w: Math.max(this.minWidth, Math.ceil(metrics.width) + this.padding * 2),