chore: Create NetEvolve.Pulse.Benchmarks project with BenchmarkDotNet

[samtrion]

User Story

As a developer optimizing Pulse performance, I want a NetEvolve.Pulse.Benchmarks project with BenchmarkDotNet, so that I can measure dispatch latency, interceptor overhead, and outbox throughput with reproducible, CI-runnable benchmarks.

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Requirements

• Create �enchmarks/NetEvolve.Pulse.Benchmarks/NetEvolve.Pulse.Benchmarks.csproj:
  • Target framework:
    et9.0.
  • Dependencies: BenchmarkDotNet, NetEvolve.Pulse (project reference), NetEvolve.Pulse.EntityFramework (project reference).
  • Program.cs: BenchmarkSwitcher.FromAssembly(typeof(Program).Assembly).Run(args).
• Add to solution.
• Benchmark classes:
  • CommandDispatchBenchmarks: SendAsync with 0/1/3/5 interceptors.
  • QueryDispatchBenchmarks: QueryAsync cached vs. uncached.
  • EventDispatchBenchmarks: sequential 1/5 handlers, parallel 5 handlers, with EventFilterInterceptor.
  • StreamQueryBenchmarks: 10/100 items with/without logging interceptor; measures time-to-first-item and throughput.
  • InterceptorOverheadBenchmarks: [Params(0,1,3,5,10)] interceptors, no-op handler.
  • OutboxThroughputBenchmarks: EF Core InMemory + SQLite in-memory, batch sizes 1/10/100.
  • RegistrationBenchmarks: manual vs. source-gen registration startup time, 10/50/100 handlers.
• Add .github/workflows/benchmarks.yml: trigger on �enchmark label or workflow_dispatch; run dotnet run -c Release; post Markdown results as PR comment.

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Acceptance Criteria

• Project builds and runs in Release mode without errors.
• All benchmark classes execute successfully.
• CI workflow triggers and posts results.