okf 0.5.0

• Adopt OKF revision 62432a0: every timestamp is an ISO 8601 datetime with a UTC offset. A date-only or offset-less value raises the non-blocking okf/timestamp-without-offset advisory naming the exact field, and OkfSpecValidation.isConformant is unchanged, so a bundle that validates today still validates. okf validate --strict is the exception: it escalates advisories to failures, so it starts failing on date-only timestamps it used to accept. Run okf format --migrate-timestamps on those bundles, or drop --strict until you have.
• Compare staleness as an instant rather than a local calendar day. stale_after was read as a calendar date and compared in the caller's local zone; it is now an instant, stale when now >= stale_after. East of UTC a concept goes stale later than before — two hours in Berlin, twelve in Auckland — and west of UTC it can now become stale on the previous local day. Callers in UTC see no change.
• Add okf format --migrate-timestamps, which rewrites date-only values to T00:00:00Z and reports every change. It is opt-in, idempotent, writes nothing under --check, and leaves offset-less datetimes alone rather than guessing a zone for them. Migrating a date-only verified.at can raise a concept's trust_tier from unverified to human-reviewed, because the verification now carries a usable time; that change is visible in okf graph.
• Reject impossible timestamps through one strict parser. 2026-02-30 previously rolled over into March 2 and was accepted; it is now rejected everywhere. Date values still read as midnight UTC for stale_after, usage_window and last_modified, where a date has always been valid. generated.at and verified[].at have always required a time, so a date-only value there carries no instant and does not count as a verification.

See the full changelog for changes in earlier releases.