Benchmark: Add MemoryDiagnoser to capture allocations #31
Description
Current: Benchmarks in tests/VbaCompiler.Benchmark/CompileVbaProjectBenchmark.cs and tests/VbaCompiler.Benchmark/CompileMacroBenchmark.cs run without [MemoryDiagnoser], so allocation/GC data is missing.
Proposed: Add [MemoryDiagnoser] to both benchmark classes (or assembly-level) so runs report allocations/GC, per BenchmarkDotNet good practices.