[LLF1-3] `Leios.Types`: the endorser block, its announcement, and the vote

[williamdemeo]

Description

New Leios primitive types for the Dijkstra specification, per the design note and CIP-164 as amended by cardano-foundation/CIPs#1250: the endorser block, its announcement, and the vote.

The certificate is deliberately absent: LeiosCert (signer bitfield plus aggregate signature) lives in the committee module introduced by #1300, and this issue coordinates with that module rather than duplicating it.

• EndorserBlock: an ordered list of transaction references, List (TxRefHash × ℕ) (hash of the complete transaction bytes plus declared size, CIP-164 Appendix B); duplicate-freedom is a validity condition, not a proof field (decision recorded during the fork trial's M1-3 review).
• hashEB: the EB identifier as the hash of the reference structure itself, via an abstract hashEBRefs; the byte-exact preimage stays deliberately unpinned (the conformance cliff tracked in the design note).
• Announcement = EBHash × ℕ: the header's announced_eb and announced_eb_size; the wire's certified_eb bit is spec-derived and not modeled.
• Vote, per the amended CIP: the hash of the announcing RB header (the signed message), the voter_id seat index, and the BLS vote signature. Consumed by no transition rule; kept as a definition serving validateVote and the quorum-safety metatheory (design-note addendum; agreed with Sebastian on Slack, 2026-08-31).
• Carrier placement, the first thing to settle in review: TxRefHash, EBHash, and hashEBRefs need a home now that the LeiosAbstract record is dissolved in favour of the core crypto structure; candidates are fields on CryptoStructure next to the BLS primitives, or parameters of this module.
• DecEq instances for all records; module prose maps each type to its CDDL counterpart (Appendix B).

Subissue of #1295.

Note. The branch for work on this issue should stack on #1300's crypto commit (the vote's signature type is BlsSig), which is another reason to split #1300.