Add Remote controller capture IPC to the host and both SDKs

remote.focus lets a controller keyboard-capture lease ask core to enter
or leave remote focus; the reply acknowledges admission only. Core
reports the actual state with remote.focus events and forwards routed
transitions as remote.input events carrying the source keycode and, on
fresh presses, a canonical key name. A full focus mailbox revokes the
lease; revocation drains pending focus work. No native capture owner is
attached yet.

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

internal/tentacle/remote.go

@@ -191,6 +191,16 @@ func (session *Session) revoke_remote_locked(reason string, notify bool) {
 			}
 		}
 	}
+	if session.remoteCapture != nil {
+	drainCapture:
+		for {
+			select {
+			case <-session.remoteCapture:
+			default:
+				break drainCapture
+			}
+		}
+	}
 	if session.remoteKeys != nil {
 	drainKeys:
 		for {
@@ -280,6 +290,8 @@ func (session *Session) remote_call_locked(method string, params json.RawMessage
 		return session.remote_present_locked(params)
 	case "remote.key":
 		return session.remote_key_locked(params)
+	case "remote.focus":
+		return session.remote_focus_locked(params)
 	case "remote.open":
 		var request tentaclewire.RemoteOpen
 		if decode_strict(params, &request) != nil || len(request.Action) != 32 || request.Epoch == 0 || !tentaclewire.ValidRoleGrants(request.Role, request.Grants) {