refactor: drop tools/ from the core library

AniparseExtract was a stub — real_main() was a `// ...` placeholder — and a raw
early copy of what is now the aniparse-cli repo. The CLI belongs outside the
core: the library is the interface, not the downloader.

Removes the directory, the ANIPARSE_BUILD_TOOLS option, the preset entry and the
codecov ignore rule. Clean static rebuild passes (567 assertions, 163 cases).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: Toilettrauma