docs(readme): align status wording with forward-only roadmap

📝 Add mandatory field-notes system and Feb 12 session gotchas

release: version 0.8.0 with async/await support

- Bump version to 0.8.0 in Cargo.toml
- Update ROADMAP.md: remove completed v0.8.0 section
- Update CHANGELOG.md: add comprehensive v0.8.0 release notes
- Update README.md: highlight async/await features
- Add architectural review notes document

Major features in v0.8.0:
- Full async/await with Promise-based concurrency
- Thread-safe Arc<Mutex<>> architecture refactor
- Thread-based async execution runtime
- Iterators and generators (completed in v0.7.0)
- Complete testing framework
- Standard library expansion

🚀 Release v0.7.0 - Core Language Completion

- Update version to 0.7.0 in Cargo.toml
- Finalize v0.7.0 release notes in CHANGELOG.md
- Update ROADMAP.md to mark v0.7.0 as RELEASED
- Update README.md status to v0.7.0 with completion message

All P0, P1, and P2 features complete! Ruff is now a fully-featured,
Python/Go/Rust competitive language with 100+ built-in functions.

🚀 RELEASE: v0.6.0

📖 DOC: Removed unreleased section

🔖 Prepare v0.4.0 release

🔖 RELEASE: version 0.3.0

- Update version in Cargo.toml from 0.2.0 to 0.3.0
- Update ROADMAP.md: v0.3.0-dev → v0.3.0 (January 23, 2026)
- Update CHANGELOG.md: Move Unreleased features to [0.3.0] - 2026-01-23
- Add version comparison links to CHANGELOG
- Release includes: JSON Support, Multi-Line Comments, Doc Comments, Array Higher-Order Functions

🚀 RELEASE: v0.2.0

🚀 RELEASE: v0.1.0