A peer downgraded from level 2 to level 1 resumes from its unrevoked level-2 floor on that handshake #1091

Problem

When a direct peer's handshake resolves originFloors level 1 after it certified at level 2, the receiver queues a revocation of the stored checkpoint-grade floor (harper-pro#922 items 3–4) but builds that same reconnect's subscription request from the floor it still holds: the resume starts at max(position, below(F)) under the level-1 contract (DESIGN item 27) once more, before the revocation lands. A downgraded binary may have written below the floor it certified, so that one resume keeps item 27's exposure.

Proposal

When the handshake downgrades a route that holds level-2 qualifiers, resume that request from the applied position only (ignore the stored floor), and let the revocation land with the first sequence update. Deferred from the checkpoint PR as pre-existing level-1 behaviour.

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Review-Deferral: 99b7bb1f135fb4aa severity=minor category=data-integrity