Brings the worktree-mooncake-layerwise line (layerwise Mooncake connector, write-mode proxy, real engine-state feed + eff_ accessors, mb7 microbench, v3 trace re-profile, A/B x migration matrix runner) into main so the repo is self-contained for these experiments. Disjoint paths (microbench/connector_tax/layerwise/*) => clean merge. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>