## What changed
- Export `GrpcCodeModeHost` as a transport-independent implementation of the
code-mode gRPC API.
- Support leased sessions, execution and wait lifecycle operations, filtered
nested tool-call subscriptions, tool completions, and notification
acknowledgements.
- Share host-wide request and active-cell limits across the existing and gRPC
transports, and bound identifiers, metadata, subscriptions, and pending
callbacks.
## Testing
- Add coverage for request conversion, ordered callback routing, cancellation,
session cleanup, backpressure, malformed input, and resource-limit handling.
GitOrigin-RevId: f146ba7e6fe4e4aa02f25dd3f961120980516d0e
