When comparing a native TypeScript checker with an older tsc, align the type environment

When comparing a native TypeScript checker with an older tsc, align the type environment before interpreting either speed or diagnostic differences. TypeScript 6 changed the default types list to empty, so a project that previously acquired ambient declarations automatically may report missing MDX modules or lose contextual parameter types. With skipLibCheck, a missing ambient dependency can also weaken checking without producing a direct declaration-file error. Explicitly restore the intended ambient packages, compare loaded application files, then repeat successful cold and cached checks. Use operating-system peak RSS rather than compiler-reported heap counters, and distinguish cache-cold from filesystem-cold runs. These steps improve benchmark validity; they do not establish complete compiler or editor parity.