manifest: unify index, row identity, and auxiliary verification report

[Fieldnote-Echo]

Motivation

As the manifest grows beyond the primary index artifact, callers need one report that clearly states what was verified, what was skipped, and what semantic bindings were enforced. This is especially important for systems that need to audit a complete artifact bundle before loading an ordvec index.

Scope

• Extend the verification report so index artifact checks, row identity checks, calibration checks, attestations, and named auxiliary artifacts have a coherent top-level structure.
• Make skipped checks explicit and machine-readable.
• Preserve stable error and warning codes.
• Include enough resolved-path and digest information for logging without requiring callers to re-open the manifest.
• Keep policy decisions outside the verifier: the report should describe verification facts, not approve a deployment.

Acceptance Criteria

• The report identifies every declared artifact and whether it was verified, skipped, missing, or failed.
• Row identity binding is reported separately from raw index-byte integrity.
• Auxiliary artifacts, if supported, are represented in deterministic order.
• JSON output is stable enough for downstream tests and audit logs.
• Documentation includes an example report for a successful manifest and a failed/tampered manifest.

[Fieldnote-Echo]

Downstream report need from ordgrep: keep primary index integrity, row identity, and auxiliary sidecar verification separate in the report, while still presenting one deterministic top-level result. The report should make skipped checks explicit and machine-readable; for example, sign.ordvec present/verified, optional artifact absent/skipped, sparse sidecar tampered, row map mismatch, etc. That lets a CLI fail closed while still emitting useful audit logs.