A throwaway-shaped browser app that checks Vellum and Ariadne saves survive a published WebAssembly build.

The trimmer and AOT compiler run only on publish, so no desktop test can show a save breaking there.  This app loads
saves of types nothing constructs in code, which is what a trimmer removes, and prints PASS or FAIL for each.

Run it with `python Scripts/wasmcheck.py`, adding `--aot` for the several-minute AOT publish.  It needs node on the
PATH.  It roots only its own assembly for the trimmer, as a game would, so it also tests the ILLink.Descriptors.xml each
Vellum and Ariadne assembly embeds.

ProbeSaves.cs holds saves written by the app itself.  A run of a build made with -p:ProbeSaver=true prints new ones
for pasting there, which is needed after a change to the saved shape of a probe type.