Add polylint and scythe

[Goldziher]

Adds two Rust static-analysis CLIs (MIT), each as a data/tools/<name>.yml:

• polylint — universal zero-dependency linter & formatter (poly/polylint/polyfmt) covering many languages with a tree-sitter fallback.
• scythe — polyglot SQL compiler and linter that generates type-safe code from SQL with schema-aware linting.

[mre]

Thanks for both submissions. Please split these into separate PRs: scythe only needs more age, while polylint also remains below the star and contributor thresholds.