feat: add mirror-display toggle to launch menu

Adds a "Mirror Display" entry that calls a helper script which finds
the first connected non-internal monitor and toggles mirroring of
eDP-1 onto it via hyprctl. Use case: plugging into a conference room
TV/projector while travelling.

Also fixes the menu's "Screenshot full" entry to capture the active
output instead of the hardcoded DP-1, matching the equivalent fix to
the Ctrl+Print keybind.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

hypr/scripts/monitor-mirror.sh

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+# Toggle: mirror the internal display to the first connected external monitor.
+# Travel use case — plug into a conference room TV/projector via HDMI, press
+# the bound key, and the external mirrors the laptop. Press again to revert
+# to the host's default monitor layout (via hyprctl reload).
+
+set -u
+
+internal="eDP-1"
+
+external=$(hyprctl monitors -j | jq -r ".[] | select(.name != \"$internal\") | .name" | head -n1)
+
+if [[ -z "$external" ]]; then
+    notify-send "Mirror" "No external display connected"
+    exit 0
+fi
+
+mirror_of=$(hyprctl monitors -j | jq -r ".[] | select(.name == \"$external\") | .mirrorOf // \"\"")
+
+if [[ -n "$mirror_of" ]]; then
+    hyprctl reload
+    notify-send "Mirror" "Off — reverted to default layout"
+else
+    hyprctl keyword monitor "$external,preferred,auto,1,mirror,$internal"
+    notify-send "Mirror" "On — $internal → $external"
+fi