lsrpc is local IPC (IDE ↔ language_server binary), not an upstream protocol.
cloudcode-pa.googleapis.com does not serve gRPC/lsrpc endpoints.
Restores antigravityRetryLoop + streamGenerateContent path which was working.
Removes antigravity_lsrpc.go (upstream caller) and lsrpc_test cmd.
Keeps lsrpc_handler.go (server side, receives IDE connections).
