Add relational pattern matcher

[MesTTo]

Adds relationalized pattern lowering and exact sidecar matching over canonical term identities.

The branch lowers encoded patterns into App_n(parent, children...) atoms, tracks user-visible variable slots, and matches complete fact roots by TermId equality. It compares the sidecar matcher against the existing product-query path for a repeated-variable pattern. This branch is stacked on the term-identity pattern helper branch.

Validation:

• cargo +nightly-2026-06-01 test -p mork --lib pattern_relations with RUSTFLAGS='-C target-cpu=native'
• cargo +nightly-2026-06-01 test -p mork --lib with RUSTFLAGS='-C target-cpu=native'
• rustfmt --check on kernel/src/pattern_relations.rs
• jscpd on kernel/src/pattern_relations.rs
• git diff --check
• normal diffstat matched git diff -w --stat