Derive Hash for hashable generated ADTs

[uurl]

Closes #16

Summary

Allow generated ADTs to participate in hash-based variable dumping when their fields are recursively hashable and deterministically printable.

Changes

• Remove the unconditional ADT exclusion from TyId::hashable().

• Continue excluding types containing floating-point values or pointers.

• Add Hash to the generated derive attributes for hashable ADTs.

• Add tests covering:

  • ADTs with primitive hashable fields.
  • Nested hashable ADTs.
  • ADTs containing floating-point fields.
  • ADTs containing pointer fields.

Rationale

The dump-variable logic already selects initialized locals using TyId::hashable(). Generated ADTs were excluded because they did not derive Hash, even when all of their fields supported hashing.

This change enables those ADTs without modifying the dumper ABI, memory model, or type-generation behavior.

Validation

• cargo fmt --check
• cargo build
• RUST_LOG=debug cargo test
• cargo test -p mir serialize_hashable_adts -- --nocapture