SampleTests and TracingTests do not compile, and no CI target builds them

[jeremydmiller]

Two test projects have rotted because nothing compiles them. Both fail on pristine origin/main (bd019dbba) — verified by building them from a clean worktree, so this is not fallout from the xUnit v3 migration (#3699).

Project	Failure
src/Samples/SampleTests/SampleTests	CS0246 — references Oakton, which no longer exists
src/Testing/OpenTelemetry/TracingTests	NU1010 — its dependencies (Subscriber2, OtelWebApi) carry PackageReference items with no version under central package management

Why it went unnoticed

Neither project is in wolverine.slnx, and neither is built by any target in build/CITargets.cs. So dotnet build wolverine.slnx — the documented pre-push check in CLAUDE.md — does not cover them, and neither does CI.

They are not alone in the first respect: nine xUnit projects are missing from wolverine.slnx:

• Samples/SampleTests/SampleTests
• Testing/OpenTelemetry/TracingTests
• the seven Testing/*.FSharpTests driver projects

The seven F# drivers do at least get built by the fsharp-codegen-compile-gate workflow. The two above are covered by nothing.

Suggested fix

1. Decide whether either project still earns its keep — SampleTests' Oakton dependency suggests it has been dead a long while.
2. If kept: repair them, add them to wolverine.slnx, and give them a CI target so they cannot rot again.
3. If not: delete them.

Worth doing either way, because "the full solution builds" is currently weaker evidence than it appears — that gap let a CS0029 in Wolverine.Http.AspVersioning.Tests (net10.0-only, built solely by its own CI target) reach CI past a clean local solution build during #3699.