Add Remote Braille IPC to the host and both SDKs

remote.braille requests and events carry a typed op under a
braille-stream lease: the controller's width and gestures for a
controlled reader, rendered cells back to its child, and cells, local
geometry and display gestures for a controller. Direction is validated
per role; a full mailbox revokes the lease. No display owner is
attached yet.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/tentacle/session.go

@@ -79,6 +79,7 @@ type Session struct {
 	remoteSpeech   chan RemoteSpeechDelivery
 	remoteKeys     chan RemoteKeyDelivery
 	remoteCapture  chan RemoteFocusDelivery
+	remoteBraille  chan RemoteBrailleDelivery
 }
 
 func (session *Session) Ready() <-chan struct{} { return session.ready }