refactor: share trace, error boundary, and proxy http helpers

Lift the trace-to-shape geometry into @tts/mesh (traceToShape/
traceToUvBounds), parameterized by scale so the web token viewer and
@tts/tabletop share one implementation. Move the CORS proxy HTTP helpers
(assetUrl, resolveAssetUrl, traceImage) into a new @tts/http package, and
make @tts/tabletop's ErrorBoundary the single source used by the web app.

This removes the duplicated ErrorBoundary, assetUrl, tabletopHttp, and
trace-to-shape code from apps/web and packages/tabletop.

packages/tabletop/src/http.test.ts

@@ -1,23 +0,0 @@
-import { describe, expect, it } from 'vitest';
-import { resolveAssetUrl } from './http.js';
-
-describe('resolveAssetUrl', () => {
-  it('passes absolute urls through unchanged', () => {
-    expect(resolveAssetUrl('https://example.com/a.png', 'harbor/parts/')).toBe(
-      'https://example.com/a.png',
-    );
-    expect(resolveAssetUrl('data:image/png;base64,AAAA', 'harbor/parts/')).toBe(
-      'data:image/png;base64,AAAA',
-    );
-  });
-
-  it('resolves a relative path against baseUrl', () => {
-    expect(resolveAssetUrl('./assets/tokens.png', 'harbor/parts/')).toBe(
-      'harbor/parts/assets/tokens.png',
-    );
-  });
-
-  it('returns the relative path as-is without a baseUrl', () => {
-    expect(resolveAssetUrl('./assets/tokens.png')).toBe('./assets/tokens.png');
-  });
-});

packages/tabletop/src/http.ts

@@ -1,53 +1,7 @@
 /**
- * HTTP helpers for loading part assets. The only coupling to the host app's
- * HTTP surface: the asset proxy (`/asset`) and the trace endpoint (`/trace`).
- * Kept as plain functions so they're testable without react-three.
+ * HTTP helpers for loading part assets. Re-exported from `@tts/http`, the
+ * shared package for the host app's proxy (`/asset` and `/trace`) handlers.
+ * Kept as a thin re-export so the tabletop's public surface is unchanged.
  */
-import { deserialize } from 'bson';
-
-/**
- * Resolve a part's asset URL. Absolute URLs (http/https, data:, blob:) pass
- * through unchanged; relative paths are resolved against `baseUrl` — the
- * directory of the part's source file (the json/yaml/markdown that defined
- * it). Without a `baseUrl`, a relative path is returned as-is.
- */
-export function resolveAssetUrl(url: string, baseUrl?: string): string {
-  if (/^(https?:|data:|blob:)/i.test(url)) return url;
-  if (!baseUrl) return url;
-  // `baseUrl` is a path relative to the games root (no scheme), so join rather
-  // than resolve as a URL. A fake origin lets `new URL` normalize `./` and
-  // `../`; the origin is stripped from the result.
-  const resolved = new URL(url, `http://localhost/${baseUrl}`).pathname;
-  return resolved.replace(/^\/+/, '');
-}
-
-/** Route an external asset URL through the proxy so three.js can load it. */
-export function assetUrl(url: string): string {
-  return `/asset?url=${encodeURIComponent(url)}`;
-}
-
-export interface TraceResult {
-  width: number;
-  height: number;
-  shape?: { outline: number[][]; holes?: number[][][] };
-}
-
-/**
- * Trace an image into a vector shape, BSON-deserializing the proxy response.
- * `mode` controls how the region is derived (`alpha`, `bw`, `color`); a
- * non-zero `offset` insets (negative) or outsets (positive) the shape.
- */
-export async function traceImage(
-  url: string,
-  mode: 'alpha' | 'bw' | 'color' = 'alpha',
-  offset?: number,
-): Promise<TraceResult> {
-  const params = new URLSearchParams({ url, mode });
-  if (offset !== undefined) params.set('offset', String(offset));
-  const res = await fetch(`/trace?${params.toString()}`);
-  if (!res.ok) {
-    const body = (await res.json().catch(() => null)) as { error?: string } | null;
-    throw new Error(body?.error ?? `Trace failed (${res.status})`);
-  }
-  return deserialize(new Uint8Array(await res.arrayBuffer())) as TraceResult;
-}
+export { resolveAssetUrl, assetUrl, traceImage } from '@tts/http';
+export type { TraceResult } from '@tts/http';

packages/tabletop/src/part.ts

@@ -4,7 +4,13 @@
  * app's `cardResolution.ts`).
  */
 import type { Part, Crop } from '@tts/bgm';
-import { rectShape, roundedRectShape, type Shape } from '@tts/mesh';
+import {
+  rectShape,
+  roundedRectShape,
+  traceToShape as meshTraceToShape,
+  traceToUvBounds as meshTraceToUvBounds,
+  type Shape,
+} from '@tts/mesh';
 
 /** Scale from mm (the format's `size` unit) to world units. */
 export const MM_TO_WORLD = 1 / 30;
@@ -67,15 +73,8 @@ export function traceToShape(
   width: number,
   height: number,
 ): Shape {
-  const { shape, width: tw, height: th } = trace;
-  const scale = Math.min(width / tw, height / th);
-  const ox = (tw * scale) / 2;
-  const oy = (th * scale) / 2;
-  const transform = (pts: number[][]) => pts.map(([x, y]) => [x! * scale - ox, (th - y!) * scale - oy]);
-  return {
-    outline: normalizeWinding(transform(shape.outline), true),
-    holes: shape.holes?.map((h) => normalizeWinding(transform(h), false)),
-  };
+  const { width: tw, height: th } = trace;
+  return meshTraceToShape(trace, Math.min(width / tw, height / th));
 }
 
 /**
@@ -88,25 +87,5 @@ export function traceToUvBounds(
   width: number,
   height: number,
 ): { minX: number; minY: number; maxX: number; maxY: number } {
-  const scale = Math.min(width / trace.width, height / trace.height);
-  const ox = (trace.width * scale) / 2;
-  const oy = (trace.height * scale) / 2;
-  return { minX: -ox, minY: -oy, maxX: ox, maxY: oy };
-}
-
-/** Ensure a ring has the requested winding. `ccw` true yields CCW (outline). */
-function normalizeWinding(pts: number[][], ccw: boolean): number[][] {
-  const isCcw = signedArea(pts) > 0;
-  return isCcw === ccw ? pts : [...pts].reverse();
-}
-
-/** Signed area of a polygon; positive means counter-clockwise. */
-function signedArea(points: number[][]): number {
-  let area = 0;
-  for (let i = 0; i < points.length; i++) {
-    const [x1, y1] = points[i]!;
-    const [x2, y2] = points[(i + 1) % points.length]!;
-    area += x1! * y2! - x2! * y1!;
-  }
-  return area / 2;
+  return meshTraceToUvBounds(trace, Math.min(width / trace.width, height / trace.height));
 }