[P2-E8.6] Air-gapped validators: standing attestation proxy (parking lot)

**Context.** Requirement from DA (2026-08-04): validators without open-internet access
need a proxy attesting that the dedicated synchronizer they use is in good standing;
assume at least one dual-connected validator, not all. Phase assignment unconfirmed —
parked here so it is tracked.

**Deliverable (when activated).** Design note: what "good standing" comprises
(registration active, fee current, reports on cadence), how the attestation is served and
verified offline.

**Acceptance.** Phase confirmed with DA; design note reviewed.

**Depends on.** P2-E3.1, P2-E6.1 (data sources).

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Epic: #71 · Plan: [P2-E8-deployment-ops.md](https://github.com/ChainSafe/canton-extending-mainnet/blob/main/docs/planning/phase-2-epics/P2-E8-deployment-ops.md)

Start with docs/planning/phase-2-epics/P2-E8-deployment-ops.md and review dependencies P2-E3.1 and P2-E6.1 for the data sources. Confirm the phase with DA before drafting the design note; done means the note defines good standing, offline serving and verification, and has been reviewed.

Written by the indexing model from the issue text.