Changelog (v2.1):
- Add comprehensive release notes for UTXO blocking mechanism
- Document new token flags (BIT 16-19)
- Document new TSD types (0x0029-0x002B)
- Describe temporal semantics (delayed activation/unblocking)
- List CLI command updates
- Include compatibility, performance notes
- Mark as unreleased until final release

README.md:
- Restructure with table of contents and sections
- Add Features overview
- Highlight new UTXO blocking mechanism
- Include quick example code
- Document build instructions and options
- Add documentation links
- Include contributing guidelines
- Reference to UTXO_BLOCKING_EXAMPLES.md

Both files provide clear overview of v2.1 features for users and developers.