Narrows the 3.7.0 slice to the feature users actually get: RFC 003 agent
coordination (events, artifacts, patch handoffs) plus the multi-master
logstream sync that makes it work across machines.
Removed, deferred with the rest of RFC 004:
- replica_sync.py / vector_cache.py and the `mempalace replica` CLI
- the /snapshot/* hub endpoints they backed
- website/concepts/replicated-palace.md
Memory read replicas were a leaf on the dependency graph (nothing in the
logstream path imports them), and shipping them half-done meant documenting
a mesh whose memory does not actually converge. Dropping them lets the docs
say one true thing instead of two hedged ones: coordination syncs, memory
stays local, point every agent at one hub if you want shared recall.
Fixes a bug found by running it: _start_peer_sync_thread() read peers.json
once at startup and returned early when absent, so a hub started before
peers.json was written never synced — silently, forever. That is the order
the guide tells users to follow. Membership is now re-read every round.
Verified on two live hubs: delegation loop end-to-end, verbatim patch
round-trip by sha256, bidirectional sync, CLI sync alongside a live hub,
and automatic convergence 15s after writing peers.json with no restart.
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