Evidence evaluation lacks an issuer axis: verifiers cannot require who issued a chain

[y1o1]

Problem

A verifier has no normative way to require conditions on who issued a chain it accepts.

• The EvidenceView manifest spine is (BodyAddress, WireVariantID) pairs and carries no issuer axis.
• A decision profile is {ID, RequiredScopes[]} — it can only require scopes, so the "what a verifier requires" layer is under-provisioned for issuer identity.
• SOURCE_CREDENTIAL_ATTESTATION@1 counts authenticity (n/n), not identity, so it cannot be reused for issuer requirements.

Direction (decided)

• Add the axis on the generic side (this catalog); domain profiles supply only the value source (the domain's trust anchor). Issuer conditions belong to the policy/decision layer (claims.contract.distinct-from-profile).
• Do not add issuer to the manifest: the issuer is deterministically derivable from the body-addressed chain, so a manifest field would be redundant and a breaking change to EvidenceViewID.

Required predicates

1. chain origin is X
2. X appears somewhere in the chain
3. every issuer in the chain is within a trust set
4. no issuer outside X (only-X)

Open questions

• Name and shape of the vector-exposed field (array in spine order?).
• Assumptions above predate the 2026-08 purpose-first rebuild (D013 EvidenceView / manifest extension) — re-verify against current main before starting.