v0.8.1 — Jimeng support, Doubao fix, reproducible masks

Re-release of v0.8.0 with a packaging fix: the 0.8.0 sdist was rejected by PyPI for exceeding the file-size limit (its source distribution bundled the committed test corpora under data/). 0.8.1 excludes data/ from the sdist; the wheel is unchanged.

Visible watermark removal: Jimeng support, Doubao fix, reproducible mask build

New

• Jimeng / Dreamina (即梦AI) visible wordmark removal — remove-ai-watermarks visible --mark jimeng (or --mark auto). Reverse-alpha against a captured alpha map plus a thin residual inpaint, NCC-aligned across resolutions. (#13)

Fixed

• Doubao "豆包AI生成" removal left a readable outline on real images. The detector was fooled by the thin outline (so it reported success) while the mark stayed visible. Rebuilt the alpha map (careful gray-self solve), always NCC-align, thin residual inpaint, and a wider locate box now reduce it to faint texture-level traces.

Changed

• Gemini sparkle assets rebuilt from our own controlled captures (validated NCC 0.9998 vs the prior third-party asset); removal behaviour unchanged.
• New scripts/visible_alpha_solve.py reproducibly rebuilds all three visible-mark alpha assets from committed solid-colour captures.
• Clarified SynthID labelling in identify ("SynthID watermark, inferred from C2PA metadata").