Inline Ty indices: replace ty(Int) references with actual type data

[Stevengre]

Problem

Type information in the K semantics is accessed indirectly through Ty indices (ty(Int)). Every time type data is needed, a lookupTy(TY) call retrieves it from the type table.

This indirection:

• Adds complexity and reduces readability of semantic rules
• Creates extra simplification overhead for the Haskell backend

Proposal

Inline all Ty indices to actual type data, eliminating the lookupTy indirection layer.

The inlining could be done at the Python layer or at the stable-mir-json level. Recursive types (e.g., self-referential structs) are not a blocker — the current system already has mechanisms like typeof to express them.

Scope

TY / lookupTy appears ~81 times across the semantics files, primarily in:

• rt/data.md, rt/types.md, rt/value.md
• kmir.md, intrinsics.md

Acceptance Criteria

• All lookupTy(TY) calls eliminated or replaced with direct type data
• Existing tests pass