Verify against a real Frame; switch clipboard to Klipper

The headset desktop is nested Plasma in gamescope with no wl-copy/xclip,
so paste-to-frame.sh now calls Klipper over plasmashell's D-Bus bus.
connect.sh, push.sh, paste-to-frame.sh and install-apps.sh were exercised
on SteamOS 0.3.0 (build 20260922); docs record what was confirmed.
Cross-provider review skipped at Alex's request (Astra quota exhausted).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

scripts/push.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env zsh
 # Mac-side: copy a file or folder to the Steam Frame.
 #
-# UNTESTED against real hardware.
+# Verified on a Frame 2026-09-25.
 #
 # Usage: scripts/push.sh SOURCE [REMOTE_DEST]   (default dest: ~/Downloads/)
 set -euo pipefail