M5I08: MVP+2 extensions (Unix sockets, CPU affinity, HTTP compliance, signals)

[s2x]

What it builds

Smaller platform and HTTP features deferred to MVP+2:

• Unix socket support (AF_UNIX): proxy option for unix:///path instead of TCP
• CPU affinity: WorkerConfig::cpuAffinity(array $cores) — Linux sched_setaffinity, no-op elsewhere
• HTTP query string: parse URI query → $request->getQueryParams()
• HTTP Expect: 100-continue: send 100 Continue before reading large body
• Correlation headers: X-Request-Id (UUID), Server-Timing (W3C), X-Worker-Pid
• SIGUSR1/SIGUSR2: reopen logs, dump stats, graceful rolling restart

References

• Follow-up MVP+2 M1I07: MasterProxy (SCM_RIGHTS) #9-14
• Milestone doc: docs/superpowers/milestone-5/08-mvp2-extensions.md