feat: complete M8 replication primitives + forage enhancements + docs
Milestone 8 (phases 1-4):
- Shard-aware WAL segment naming, BatchHeader v2, ShardRouter
- Transport trait, InProcessTransport, WalShipper, FollowerDb
- HLC, PNCounter, LWWRegister, CrdtSignalState, ReconciliationEngine
- Session replication bridge with SeqNo/HWM, idempotency store
Forage application:
- Multi-source discovery engine with MAB exploration
- Embedding-based label system, server handlers, UI refresh
Other:
- QUICKSTART.md, README.md, milestone-8 planning docs
- Hard negative union semantics, RLHF export enhancements
- Recovery benchmark and visibility test expansions
- Split 8 oversized source files per CODING_GUIDELINES §9
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>