docs: update CLAUDE.md with verified build and test commands

Remove template UnitTest1.cs placeholder. Add actual project structure,
run commands for the NATS server host, and update test command examples
to reference the real project paths.

tests/NATS.Server.Tests/UnitTest1.cs

@@ -1,10 +0,0 @@
-namespace NATS.Server.Tests;
-
-public class UnitTest1
-{
-    [Fact]
-    public void Test1()
-    {
-
-    }
-}