feat(database.do): Comprehensive README with cascading generation

- Relationship operators: -> ~> <- <~ with modifiers (? [])
- Blog example showing cascading: Blog -> Topics -> Posts
- Semantic Nouns & Verbs from ai-database
- Natural language queries: db.Lead`ready to close`
- Promise pipelining with batch relationship loading
- ForEach with durability and crash recovery
- Events, Actions, Artifacts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: nathanclevenger