BIP85: Add Codex32 as application 93'

This allows wallets to derive codex32 secrets and codex32 shares from BIP-0032 master keys.

Summary of changes

• Add codex32 application
• Add BIP-0093 to references
• Bump version number to 1.4.0
• Add 1.4.0 reference implementation

Rationale

• Mirrors the existing BIP-85 application for BIP-39.
• Codex32 offers error correction, hand verification, identifiers, and secret sharing improvements vs BIP-39.
• Deterministic generation produces auditable backups by avoiding reliance on local RNG, helping users who distrust device entropy.

Specification

• Adds Application 93' to BIP-0085 using derivation path:

m/83696968'/93'/{header}'/{byte_len}'/{index}''

Tests Reference tests and new vectors will be included in the reference bipsea implementation: https://github.com/benwestgate/bipsea/compare/master...BenWestgate:bipsea:master

Mailing List Discussion: https://groups.google.com/g/bitcoindev/c/--lHTAtq0Qc

Status Ready for conceptual and approach review. This change is additive and does not modify existing BIP-85 behavior.