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/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));
 }