Remove paste from definition rule composition

[adampetro]

Summary

This change makes definition rules and visitors more consistent with the executable rules and visitors. Both validation surfaces now use the same tuple composition and construction patterns.

• replace combine_definition_rules! with tuple-based rule composition
• use seq_macro implementations for definition rule and visitor tuples
• move definition rule construction to Visitor to align validation surfaces
• remove the unused iterator macros and the paste dependency

Testing

• cargo check --workspace --all-targets
• cargo test -p bluejay-validator
• cargo test -p bluejay-validator --test definition_integration_test
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo fmt --all -- --check

Closes #134