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/connect.sh

@@ -2,7 +2,7 @@
 # Mac-side: find the Steam Frame, create a key, add a `Host frame` alias to
 # ~/.ssh/config, copy the key, and optionally disable SSH password logins.
 #
-# UNTESTED against real hardware. Idempotent: safe to re-run.
+# Verified on a Frame 2026-09-25 (except --harden). Idempotent: safe to re-run.
 #
 # Usage:
 #   scripts/connect.sh [HOST_OR_IP]          # set up key + alias