When replaying old CRDT ops that predate new struct fields (e.g.
claimed_by, claim_ts added by story 479), node_from would call
.unwrap() on None and panic during init. Now defaults to an empty
CrdtNode::new() for missing fields, allowing schema evolution without
breaking replay of historical ops.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Timmy