Changelog (v0.2.X)

0.2.0

[PR-2] derive_context/1 now returns {:error, :id_too_long} when a Sender or Recipient ID exceeds 7 bytes, where the NIF previously panicked. Callers that pattern-match only on {:ok, _} for an over-long ID now hit a clean error.
[PR-2] When a context sets :id_context, protect_request now emits the h flag plus the kid context on the wire (RFC 8613 §6.1), and unprotect_request rejects a mismatch with :unknown_id_context. Default output (no :id_context) is unchanged and still matches the RFC C.4/C.5/C.7 vectors bit for bit.

[PR-2] ID length is now validated at derive_context: IDs longer than the nonce allows (7 bytes) return {:error, :id_too_long} instead of reaching a Rust assert! and panicking inside the NIF.
[PR-2] id_context is now wired through end to end. It was derived into the keys but discarded, so protect_request could never emit the kid context and unprotect_request never checked it.

[PR-2] Sequence-number persistence hook (RFC 8613 Appendix B.1): OSCORE.sender_seq/1 reads the Sender Sequence Number counter and derive_context's :sender_seq option restores it, so the counter can survive a restart and the same AEAD nonce is never reused under the same key.
[PR-2] Added a debug_assert documenting the <= 8-byte invariant in be_bytes_to_u64.