Type Alias AccountIdentityProofRejectReason

The reason a 0x8009 account identity proof (or a GroupContext/KeyPackage location check) was rejected. One literal per spec validation step — never a coarse bucket. The nine D-13 minimum reasons (invalid-location, missing-support, missing-data, duplicate-data, ciphersuite-mismatch, signature-key-mismatch, identity-mismatch, invalid-proof, legacy-extension-present) are all present; invalid-credential, invalid-dictionary, legacy-group, mixed-profile, and missing-requirement are the additions D-13 allows.

Phase 9 (UPD-01) adds two more, both emitted by the commit-legality bucket classifier in ./integrity.js, not by any validator in this module:

• member-identity-changed (D-05): the replacement leaf at an existing member's index carries a different account identity than the leaf it replaced. Deliberately NOT identity-mismatch — that literal means the proof's signer does not match this leaf's own credential identity (a single-leaf check). Conflating the two would collapse a membership-model violation into a proof-binding error.
• unattributable-leaf (D-02): a changed leaf that, with the commit's full proposal list and committer index available, matches no Add proposal, no Update proposal sender, and is not the committer's update-path leaf — fail closed.