[igorbernstein2]

Clarifies the Session lifecycle, cancelRpc, and server heartbeat/deadline contracts in Session and SessionImpl:

• Fix misleading Javadoc on Session.close() (which previously described immediate abort like forceClose() rather than graceful drain via CLOSING -> WAIT_SERVER_CLOSE) and document how each SessionState is bounded.
• Document in SessionImpl.cancelRpc() and SessionImpl.close() why currentRpc remains set after local cancellation until the server replies (the protocol does not yet have a wire cancel-vRPC message, so keeping currentRpc set prevents returning a READY session to the pool while the vRPC is still active on the server and prevents sending CloseSessionRequest while a vRPC is still in flight on the server).
• Document in SessionImpl.checkCloseTimeout() why closeTimeout only needs to bound WAIT_SERVER_CLOSE (CLOSING only occurs while a vRPC is active on the wire, which is bounded by server heartbeats via checkHeartbeat() and the server-enforced VirtualRpcRequest.deadline).

[gemini-code-assist]

Code Review

This pull request enhances the documentation and inline comments in Session.java and SessionImpl.java to clarify the Session V3 protocol state transitions, graceful close behavior, RPC cancellation mechanics, and timeout handling. Specifically, it explains why a session waits in the CLOSING state during active vRPCs and details the server-side invariants bounding this state. There are no review comments, and I have no additional feedback to provide.