feat: implement source IP affinity for cluster workers

[rockyshi1993]

Implement actual TCP source-IP affinity for cluster.sticky: "ip", replacing the previous round-robin placeholder. Master selects stable Worker slots with rendezvous hashing and hands paused sockets over a bounded offer/prepare/commit protocol. All five built-in adapters and their official factories use the shared Node HTTP receiver; Fastify uses its public serverFactory. The default remains sticky: "none".

Workers entering local application shutdown withdraw new-connection eligibility before closing resources, while in-flight connections keep the existing shutdown budget. Local exits retain automatic recovery in the same slot; Master-initiated draining does not create duplicate replacements. Readiness is rechecked immediately before slot activation, and forceClose errors are recorded without skipping subsequent cleanup. Chinese guidance and English guidance describe the matching behavior and IPC contract.

Validation:

• Final Node 20 and Node 22 regressions: 307 tests passed on each runtime, including real socket handoff across all five adapters, rolling replacement, local shutdown, recovery policy, generation checks and late readiness.
• The partial-header shutdown test verifies actual Worker forceClose and normal Worker exits before Master fallback. A separate SIGSTOP case verifies Master SIGKILL protection. Portable local-shutdown regressions run on Windows; Unix signal and source-IP fault cases use explicit platform skips.
• Framework ESM/CJS builds, type checks, lint, formatting, the 1,216-entry public-surface check and documentation source/IPC contracts passed.
• Full remote validation for 818baeb148e0f87efbfeb4b94c2c2f30930f9601: CI run 38003622430, passed all 16 jobs. The full coverage run passed 4,469 tests (2 conditional skips) across 228 files with the existing thresholds. Windows passed 158 tests with 5 platform skips, including the new local-shutdown and Worker force-close regressions.

No package version or tag changes are included.