Remote worker sessions gain sender attestation checks

What

• Remote/hosted-worker session transport now tracks a workerAttestationPolicy, set via a new setWorkerAttestationPolicySink callback, and reacts when that policy reports a fault.
• A new unattested_request outcome was added: it appears in tool-call outcome tracking alongside unknown_call, no_approval, stale, queue_full, rate_limited, and duplicate_call, and is shown to users in Remote Control/device-linking error explanations when a machine's account requires sender attestation that the service couldn't verify.
• The method that judges inbound session-channel frames (renamed from dropsUnverifiedSessionChannelFrame to sessionChannelFloorVerdict) now returns one of three outcomes, "passed", "dropped", or "refusal_rebuilt", instead of a plain true/false, and a new judgeInboundFrame step classifies frames against the attestation policy.

Why

This adds a way to detect and reject remote tool calls or session frames that can't be verified as coming from an attested sender, surfacing a clear reason instead of failing silently or ambiguously.