Add a decimals option, fix dropdown overflow and the texture filter

- NumberField takes a decimals option (default 3); frame rects and the
  slice dialog use 0, matching their integer model.
- Button truncates its label to the drawn width; Dropdown reserves the
  chevron slot. NodeView reuses the shared truncate().
- Setting scaleMode leaves the style's shared resource id in place, so
  the old GPU sampler stayed in use until a reload. Call style.update().
- Graph gets a header bar like the Texture tab: GraphEditor is now the
  frame, the former editor is GraphCanvas. A selection the tab does not
  concern no longer unloads the behavior.
- New e2e step 14 guards text overflow across all widgets.

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

src/core/properties/PropertySchema.ts

@@ -7,7 +7,22 @@ import type { PropertyBag, PropertyValue } from '../model/Properties';
  * these entries, so adding a property to a type is a single line in a schema below.
  */
 export type PropertyDef =
-  | { key: string; label: string; kind: 'number'; default: number; min?: number; max?: number; step?: number }
+  /**
+   * `decimals` is the number of places the field displays; it belongs only on properties that
+   * are integral by their meaning (counts, indices). Geometry does not qualify: dragging in the
+   * viewport puts fractions into a position or a size, and a field that hid them would commit
+   * the rounded number back into the project.
+   */
+  | {
+      key: string;
+      label: string;
+      kind: 'number';
+      default: number;
+      min?: number;
+      max?: number;
+      step?: number;
+      decimals?: number;
+    }
   | { key: string; label: string; kind: 'text'; default: string }
   | { key: string; label: string; kind: 'color'; default: number }
   | { key: string; label: string; kind: 'boolean'; default: boolean }