Floor tracking for A2A multi-turn exchanges

Determine whether floor state should be tracked for A2A multi-turn exchanges by using contextId as a pseudo-conversation.

Background

The Agent Status Protocol tracks floor states per conversation and currently aligns this dimension with the Open Floor Protocol. Agent2Agent (A2A) supports task and context identifiers but does not natively provide an equivalent floor-state model. The unresolved issue is whether contextId can serve as a sufficiently reliable proxy for a conversation in multi-turn A2A interactions.