Intermediate Representation

Curated umbrella import for TorchLean's op-tagged intermediate representation.

Use this for graph syntax, shape and element-type checks, homogeneous and heterogeneous semantics, FloatLib binary conversions and their correctness theorem, compositional proof rules, shape-soundness results, and pretty-printers. Internal code can import the individual NN.IR.* modules when it needs a smaller dependency footprint.