The agent always talks to a *Conn (never a *Server directly).
Replace the Runner interface with the concrete type throughout:
- Runtime.ToolServer is now *toolsrv.Conn
- BuildRuntime takes *toolsrv.Conn
- session.Config, SessionInfra, InfraConfig use *toolsrv.Conn
- All inline type assertions in agent.go deleted — methods called
directly on *Conn (SetEnv, SetCWD, Close, Detach, ListDetachedRaw,
SignalDetached, GetDetachedOutput, DismissDetached, SetAllowTools,
SetOnToolsChanged, Ping, ToolRegistryRevision)
- Added Conn.ToolRegistryRevision() that returns 0 (remote connections
don't support revision tracking; use push-based OnToolsChanged instead)
- Deleted the Runner interface and its test
- Renamed LoadToolOnRunner → LoadToolOnConn