caveman engine/pixel third-party notices

This package is a Go port of pxpipe (https://github.com/teamchong/pxpipe),
a text→PNG token compressor for LLM requests, used under the MIT License:

  Copyright (c) 2026 claude-image-proxy contributors

MIT License notice:

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

Glyph atlas fonts
-----------------

The embedded glyph atlases under assets/ are rasterized bitmap derivatives of
two fonts, generated by pxpipe's build-time atlas generator and carried here as
binary assets. The atlases are not distributed or named as fonts themselves.

- Spleen 5x8 — Copyright (c) 2018-2026, Frederic Cambus. BSD 2-Clause License.
  Full text: assets/SPLEEN_LICENSE.txt

- GNU Unifont 16.0.04 — dual-licensed under the SIL Open Font License 1.1 and
  the GNU GPL version 2 (or later) with the GNU font-embedding exception. The
  rasterized glyphs embedded here are unaltered portions of the font embedded
  into this software under those terms. Full text: assets/UNIFONT_LICENSE.txt
