release: v2.1.0 — promote from rc1 to stable

Promote v2.1.0rc1 to a full stable release. All production-hardening
fixes from the rc1 cycle are included: honest is_quantized reporting,
architecture fallback fixes, pre-quantized repo detection, expanded
model family support, real CI pipeline, and PEP 621 packaging.
Co-authored-by: monkeycode-ai <monkeycode-ai@chaitin.com>
Co-authored-by: monkeycode-ai <monkeycode-ai@chaitin.com>

Add MIT License to the project

Update high_level.py