0.0.41

Added

• !MergeEntity {absorbed, into, reason, evidence} applies (story:merge-entity-applies, design
  § 111, ADR 0018): it joins a duplicate node to the node it duplicates — of one type, or of types
  related through parents — in a revision of its own. The absorbed node leaves the head into a
  supersession record naming into, as a SupersedeNode retires a node, and every reference to it
  is rewritten in place: each edge at it keeps its id and runs to into, an edge joining the two is
  retired into the record, and one duplicating an edge into holds, with equal properties,
  collapses onto it; each assertion about it, naming it as its object or in a NodeRef inside its
  value, names into, every other byte unchanged; each NodeRef naming it in a node's or an edge's
  properties names into; and a property only it holds moves to into. The record's merge
  lineage — under superseded in ekr snapshot — says what moved. The absorbed node reads as a
  superseded node does; /changes lists the merge as a NodeMerged change, counted in
  nodes_merged, with into in target. Applied under every validation profile. Refused by name:
  merge-into-itself, unresolved-node, node-superseded, merge-without-reason,
  merge-without-evidence, merge-evidence-unknown, merge-types-unrelated,
  merge-undeclared-property, merge-property-conflict, merge-duplicate-edge-conflict,
  merge-self-relation (an active relation assertion joining the two nodes, either way: retract
  it first), edge-endpoint-type, wrong-type, edge-cardinality, property-cardinality and
  superseded-node-named-in-transaction. The bare {absorbed, into} shape is refused as before,
  unsupported-operation, under every profile, so retained rejections replay; a store that never
  merges keeps its roots and checkpoint bytes. ekr compare compares a merged node's lineage in
  its superseded category. The SDK builds the bare shape with EntityMerge::bare, reads
  SnapshotSupersededNode::merge and ChangeKind::NodeMerged, and Resolver::observe drops every
  cached answer naming a node a committed merge absorbs.

Changed

• Breaking: the SDK's EntityMerge::new(absorbed, into, reason, evidence) takes the reason
  and the evidence, no longer only the two nodes, and builds the shape that applies; a caller that
  wrote EntityMerge::new(absorbed, into) for the bare P1 shape writes EntityMerge::bare(absorbed, into), which every profile still refuses.
• Breaking: EntityMerge is no longer Copy, in the SDK (ekr_sdk) and in the kernel
  (ekr_kernel): each gained reason: Option<String> and evidence: Option<BTreeSet<EvidenceId>>.
  A caller that copied one clones it.