fix(autoswitch): WorkspacesChanged output-set diff; unit paths; deploy symlinks

- niri 26.04 has no hotplug event: OutputConfigChanged is only an ACK
  (niri-ipc). Watch WorkspacesChanged, diff sorted output set, apply on
  change. Proven live: eDP-1 off/on -> 3 output-set transitions, each
  matched + applied + reloaded.
- unit: %h/.local/bin/desk-autoswitch.sh, quoted Environment, drop
  User/Group (user unit); add desk-autoswitch.sh bin symlink
- desk.sh: silence validate/load-config/notify stdout
- deploy.sh: deploy repo symlinks (find -type l), so .local/bin links land
- docs: event semantics corrected (displays diagram, log)

dotfiles/zz-blankpad/.config/systemd/user/blankpad-desk-autoswitch.service

@@ -5,15 +5,13 @@ ConditionHost=blankpad
 
 [Service]
 Type=simple
-User=%u
-Group=%u
-ExecStart=/usr/bin/env bash %h/.omp/scripts/desk-autoswitch.sh watch
+ExecStart=%h/.local/bin/desk-autoswitch.sh watch
 Restart=on-failure
 RestartSec=5
 StandardOutput=journal
 StandardError=journal
 Environment=DESK_NIRI=/usr/bin/niri
-Environment=DESK_NOTIFY=noctalia msg notification-show
+Environment="DESK_NOTIFY=noctalia msg notification-show"
 
 [Install]
 WantedBy=default.target