The BaseExecutor's buildUrl() and buildHeaders() methods only handled
openai-compatible-* providers but not anthropic-compatible-* providers.
This caused Anthropic-compatible synthetic providers to fail API testing
by hitting the wrong endpoint (returning documentation instead of valid
API responses) and using incorrect auth headers.
Changes:
- Added buildUrl() handling for anthropic-compatible-* providers
to append /messages path
- Added buildHeaders() handling for x-api-key header and
anthropic-version for anthropic-compatible providers
Fixes #XXX
Co-authored-by: Bitgineer <bitgineer@bitgineer.shop>