Add tag validation to `StateUtils#unwrap`

`StateUtils#unwrap` currently skips the protobuf tag without validating it. This allowed a bug in `VirtualMapStateImpl` where `pushQueue`/`popQueue` wrapped queue metadata with `stateId` instead of `STATE_VALUE_QUEUE_STATE` (8001) — the mismatch went undetected because `unwrap` never checked what it was unwrapping.

Add an `expectedTag` parameter to `unwrap` so callers declare which field number they expect, and throw `IllegalStateException` on mismatch. Update all call sites in `VirtualMapStateImpl` to pass the appropriate tag (`stateId` for elements/singletons/kv, `STATE_VALUE_QUEUE_STATE` for queue metadata).

Start with StateUtils#unwrap and the unwrap call sites in VirtualMapStateImpl. Trace the element, singleton, key-value, and queue-metadata paths to confirm which expected tag each caller should provide. Done means mismatched tags throw IllegalStateException and all listed callers pass the appropriate tag, including STATE_VALUE_QUEUE_STATE for queue metadata.

Written by the indexing model from the issue text.