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.
Add @tts/mesh, a package for generating extruded tile meshes from 2D
shapes. It provides shape generators (rect, hex, circle, rounded rect,
frame), earcut-based tessellation of top/bottom faces with UVs, and
outward-normal wall generation, combined into raw BufferGeometry-ready
typed arrays.