0.0.39

Added

• !SupersedeNode {node, by, reason, evidence} retires a duplicate node in favour of the node
  that replaces it, in a revision of its own (story:supersede-node, design § 110). The node and
  every edge at it leave the head and are kept in a supersession record — the node and its edges
  as they were, by, the revision, the reason and the evidence — which ekr snapshot lists under
  superseded; assertions about it are not changed, and every earlier revision still reads it.
  Every head read omits it. ekr resolve of its type and one of its aliases answers by, even when
  by is of another type, and those aliases stay taken (alias-already-exists). A read of its id
  at the head — /node/<id> in either format, /expand, the MCP describe_node and expand, the
  session's — is refused as ekr.views.NodeSuperseded, naming by; /changes lists the
  supersession as a NodeSuperseded change, with the node kept in target. Refused by name:
  supersede-unknown-node, node-already-superseded, supersede-into-itself,
  supersede-by-unknown-node, supersede-by-superseded-node, supersession-without-reason,
  supersession-without-evidence, supersession-evidence-unknown and
  superseded-node-named-in-transaction; a later operation naming a superseded node or a retired
  edge is node-superseded, naming by. Applied under every validation profile. The SDK builds
  it (NodeSupersession) and reads SnapshotGraph::superseded and ChangeKind::NodeSuperseded.
  A store that never supersedes keeps its roots and checkpoint bytes. A read that reaches an
  assertion naming a superseded node names its pointer: subject_superseded_by and
  object_superseded_by in ekr sample and ekr explain, object_superseded_by on every rendered
  assertion (SDK SampledFact, ViewAssertion, SnapshotAssertion). /timeline of a superseded
  subject is ekr.views.NodeSuperseded; ekr compare compares the records as a superseded
  category, listed only where either store holds one. ekr apply-extraction replaces a value
  under a superseded key on the node kept, and a fact refused after resolving through a
  supersession to a node of another type names it.