feat: Sprint 1 Phase 2 - testing and reliability refactor

[fr3on]

Description

Comprehensive update of unit tests, implementation of specialized mocks for FFI, and PHPStan optimization for core components.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have added tests that prove my fix is effective or that my feature works
• New and existing tests pass locally with my changes (composer test)
• PHPStan reports no errors (composer analyze)

[github-actions]

🚀 Quill Performance Metrics

Environment: Ubuntu · PHP 8.3 · quill-core 0.0.2 · 2 workers Quill Core

Quill Binary Benchmark
  > Server     : Quill Core
  > Tool       : wrk
  > Duration   : 5s
  > Connections: 50
  > Workers    : 2
  > Starting Quill server...
  > Server is ready. Running benchmarks...
    Running 5s test @ http://127.0.0.1:8080/hello
      2 threads and 50 connections
      Thread Stats   Avg      Stdev     Max   +/- Stdev
        Latency     1.05ms    0.88ms   6.05ms   76.34%
        Req/Sec    25.27k     7.20k   38.62k    59.00%
      251594 requests in 5.01s, 38.87MB read
    Requests/sec:  50259.57
    Transfer/sec:      7.76MB

  > Benchmarks completed.