crucible 0.44.0

Seven more vendors, the newest OpenAI and Anthropic models, and /fast for
a vendor's faster tier. Meta, xAI, DeepSeek, Z.ai, Qwen, MiMo and MiniMax
join as rows of /login, /model lists what your credential serves, and
crucible asks once before sending anything to a vendor that may train on it.
The Windows sandbox helper no longer sees your provider keys, and --continue
resumes your latest session whichever build wrote it. Before rolling back to
0.43.3, set provider to one it serves and delete "fast": true and the
contentUse block from your configuration file.

Full changelog: v0.43.3...v0.44.0

Every change in this release is listed in CHANGELOG.md.