fix: use dynamic ports in all network tests

[cs01]

Summary

• fixes ws e2e test timeout under load (5s→15s, was failing at concurrency 32)
• all network test fixtures now accept -p PORT cli arg instead of hardcoded ports
• all test harnesses use os-assigned ports (port 0) — safe for concurrent agents
• server wait timeouts increased from 5s to 10s across all http server test suites

Test plan

• all 461 tests pass with 0 failures, 0 skipped
• network tests pass in isolation
• network tests pass when all 4 http server suites run concurrently
• ws e2e test passes under full test suite load