fix: do not treat `Float` literals as interpreted values in `grind`

This PR fixes `grind` producing proofs that the kernel rejects when the same `Float` or `Float32` value is written in different ways, such as `2` and `2.0`.

`grind` expects interpreted values to have a unique normal form, but there are no simprocs for normalizing float literals yet. `grind` now treats `Float` and `Float32` literals as uninterpreted terms.

Closes #15605

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>