@foxbook/sdk-claim v0.2.0

verified_signing_key_hex on the verified branch + structured reason_code on the unverified branch. Closes two public commitments
from A2A Discussion #1803 (cloakmaster, 2026-04-30 + 2026-05-01). Paired with tl-leaf v1.2 signing-key-registration shape (PR #60) for the rotation transition window.