openbim-step 0.6.1

Added

• Opt-in reference-integrity diagnostics (#4):
  ParseOptions::check_references(true) reports every data record whose
  instance id was already defined (DiagnosticKind::DuplicateId, on the
  later record) and each distinct id a record references that no record in
  DATA defines (DiagnosticKind::DanglingReference, on the referencing
  record). Forward references are legal (ISO 10303-21:2016 §11.2) and are
  resolved at ENDSEC. Ids compare numerically, so #07 is #7, including
  ids beyond 64 bits. Works for parse_with and the streaming
  parse_events_with alike. Nothing is dropped, so these diagnostics keep
  ParseOutcome::is_lossless true.
• Diagnostic::kind and Diagnostic::instance, and the DiagnosticKind
  enum (SkippedRecord, DuplicateId, DanglingReference).

Changed

• ParseOutcome::is_lossless is now true unless a record was skipped;
  reference diagnostics do not count as loss. Only possible to observe with
  the new option enabled.

Measured on 100 MB files (1.0–1.5 M records, median of 5): enabling the
check adds 26–33% to parse_with. Off by default, so existing callers pay
nothing. Across the 757-file on-disk corpus it flags exactly one file:
buildingSMART's IFC4 Add2 annex example wall-elemented-case.ifc, whose
#154 references #161, which the file never defines.