EXCTOOLZ vectorizer worker

Potrace JavaScript, Copyright (C) 2001-2013 Peter Selinger; JavaScript port by kilobtye. GPL-2.0.
Source supplied by the user as a standalone HTML vectorizer.

The tracing and color quantization sources are preserved in potrace.js and color-vectorizer.js. worker.js adds bounded input validation and message-based tracing. React workspace integration is in src/components/vectorizer.tsx and src/lib/vectorizer-browser.ts in the source distribution.

COPYING.txt contains the complete GPL version 2 text. The software license does not apply to artwork or SVG outputs.

EXCTOOLZ precision changes: preserve small contours (turdsize 0), lower curve optimization tolerance to 0.08 and protect sharp direction changes from 80 degrees. UI defaults to 16 ink colors, supports up to 16 and preserves source transparency through vector luminance-mask paths. White removal is opt-in.