Non-prop squashes appear non-functional

```fstar
#lang-pulse

ghost fn foo ()
preserves pure (squash nat)
{
()
(*
- Failed to prove pure property: squash nat
- Assertion failed
- The SMT solver could not prove the query. Use --query_stats for more details.
*)
}
```

No file or test entry point is named. Start by reproducing the supplied `#lang-pulse` example and tracing how non-prop squashes reach the reported SMT query failure; done means the `squash nat` preservation proof behaves as intended without the assertion failure.

Written by the indexing model from the issue text.