Initial public release: DWG/DXF 2D viewer sample

Standalone Vite sample composing acadrust-dwg WASM, dxf-parser, and Viewer2D.

src/viewer2d/Viewer2D.d.ts

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+// Types for the ported JS 2D engine (Viewer2D.js). Colocated so tsc resolves
+// `./Viewer2D.js` imports without allowJs. Only the methods the app uses are typed.
+export class Viewer2D {
+  constructor(container: HTMLElement);
+  /** Render a DWG/DXF parseResult. `keepView` preserves pan/zoom on re-render. */
+  load(result: unknown, opts?: { keepView?: boolean }): void;
+  /** Zoom-extents to the loaded drawing. */
+  fit(): void;
+  /** Resync renderer/camera to the container size (call after un-hiding). */
+  resize(): void;
+  onSelect(cb: (entity: unknown) => void): void;
+  setTheme(dark: boolean): void;
+  setGrid(visible: boolean): void;
+  getLayerInfo(): { name: string; colorHex: string; count: number; visible: boolean }[];
+  setHiddenLayers(nameSet: Set<string>): void;
+  getZoomPercent(): number;
+  onViewChange(cb: () => void): void;
+  startMeasure(cb: (r: { phase: string; ax: number; ay: number; az: number; bx: number; by: number; bz: number; d: number }) => void): void;
+  stopMeasure(): void;
+}