v0.2.4

Added

• Bi-temporal graph edges (P3-6). Relations now carry live validity:
  valid_from (when the fact became true — source frontmatter date, file
  mtime, or manifest added-at) and valid_to (when it stopped). Default
  relation reads return only currently-valid edges, so answers are
  contradiction-free; wiki_graph_query and ontology query --as-of answer
  point-in-time questions ("what did we believe in January?"), and edge
  provenance in graph answers carries the validity window. Relations marked
  functional: true in config (ontology.relations) are single-valued per
  source: a new contradicting edge invalidates the old one (never deletes it)
  instead of colliding — auto-applied at or above
  ontology.temporal.auto_apply_threshold (default 0.8), surfaced as a
  reviewable trust conflict below it, as are entity-level contradicts
  edges. Set ontology.temporal.enabled: false to opt out entirely.