v0.0.26

• Add IS_PRESENT and IS_NOT_PRESENT targeting operators (qfg-7jnb.3). Both are presence-only
  operators — they take only propertyName (no valueToMatch). IS_PRESENT(prop) resolves the
  dotted path against the merged context and returns true iff the path resolves AND the value is
  not null and not undefined. Empty string "", 0, and false are intentionally considered
  present (the question is "is the field set", type-agnostic). Missing intermediate keys in dotted
  paths count as not present. IS_NOT_PRESENT is the negation. Exported as OP_IS_PRESENT /
  OP_IS_NOT_PRESENT.