Anthropic gates newly released models (e.g. claude-fable-5-1) to Claude
Code >= 2.1.251; the spoofed 2.1.92 client got HTTP 400 on every request.
Bump User-Agent + billing-header version to 2.1.258 and refresh the
providers baseline snapshot.
Co-Authored-By: Claude Code <noreply@anthropic.com>