Add rdp-test.sh for diagnosing the RDP auth failure

xfreerdp gives far more specific error output than GNOME Connections'
generic "Authentication failed: connection failed" message. Run on
the travel laptop, writes output to rdp-test-output.txt in this same
repo so it can just be committed/pushed back rather than pasted.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

rdp-test.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+# Run this on the TRAVEL LAPTOP (t14s), in this repo's local clone, in a
+# normal local terminal - NOT inside a Remote-SSH window, since that one runs
+# on the home machine and wouldn't test the real client-side path.
+#
+# xfreerdp runs interactively (usual password prompt, and possibly a "do you
+# trust this certificate?" prompt - accept it, that's the expected
+# self-signed cert). Output is captured to rdp-test-output.txt in this same
+# directory - git add/commit/push it and it'll show up on the home machine.
+#
+# Edit RDP_USER below to the username you actually set with grdctl.
+
+set -uo pipefail
+
+RDP_HOST="teemu-thinkpad-ubuntu.tail27b01.ts.net"
+RDP_USER="CHANGE_ME"
+
+which xfreerdp >/dev/null 2>&1 || sudo apt install -y freerdp2-x11
+
+echo "Connecting to $RDP_HOST as $RDP_USER ..."
+xfreerdp /v:"$RDP_HOST":3389 /u:"$RDP_USER" /cert:ignore 2>&1 | tee rdp-test-output.txt
+
+echo
+echo "Written to rdp-test-output.txt - git add/commit/push it."