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)

scripts/desk-autoswitch.sh

@@ -1,6 +1,12 @@
 #!/usr/bin/env bash
 # scripts/desk-autoswitch.sh — hotplug daemon: apply the matching desk profile
-# whenever niri reports an OutputsChanged event.
+# when the SET OF OUTPUTS changes.
+#
+# niri has no dedicated hotplug event (verified on 26.04):
+# - WorkspacesChanged carries every workspace's `output`, so the sorted
+#   unique set of outputs changes exactly on connect/disconnect.
+# - OutputConfigChanged is only an ACK that an IPC/config output change was
+#   Applied (niri-ipc), NOT a hotplug signal.
 #
 # Usage: desk-autoswitch.sh watch
 #
@@ -8,7 +14,7 @@
 #   DESK_AUTO_HOSTNAME  only run on this hostname (default: blankpad)
 #   DESK_SCRIPT         path to desk.sh (default ~/.local/bin/desk.sh)
 #   DESK_NIRI           niri binary (default niri)
-#   DESK_DEBOUNCE_S     debounce window in seconds (default 1.5)
+#   DESK_DEBOUNCE_S     min seconds between applies (default 1.5)
 
 set -euo pipefail
 
@@ -17,8 +23,10 @@ DESK="${DESK_SCRIPT:-$HOME/.local/bin/desk.sh}"
 NIRI="${DESK_NIRI:-niri}"
 DEBOUNCE="${DESK_DEBOUNCE_S:-1.5}"
 
-usage() {
-  sed -n '2,12p' "$0" | sed 's/^# \{0,1\}//'
+usage() { sed -n '2,18p' "$0" | sed 's/^# \{0,1\}//'; }
+
+outputs_from_event() { # $1 = one JSON event line
+  jq -r '[.WorkspacesChanged.workspaces[]?.output // empty] | unique | join(" ")' <<<"$1" 2>/dev/null || true
 }
 
 watch_mode() {
@@ -26,16 +34,20 @@ watch_mode() {
   echo "desk-autoswitch: initial match"
   "$DESK" match --apply || true
 
-  local last=0 now
+  local seen="" last_seen="" last=0 now
   # One JSON event per line; reconnect forever (niri restart drops the stream).
   while "$NIRI" msg --json event-stream 2>/dev/null | while IFS= read -r line; do
     case "$line" in
-      *OutputsChanged*)
+      *WorkspacesChanged*)
+        seen="$(outputs_from_event "$line")"
+        [ -n "$seen" ] || continue
+        [ "$seen" = "$last_seen" ] && continue
+        last_seen="$seen"
         now="$(date +%s.%N)"
         # swallow bursts inside the debounce window
         if awk -v l="$last" -v n="$now" -v d="$DEBOUNCE" 'BEGIN { exit !(n - l >= d) }'; then
           last="$now"
-          echo "desk-autoswitch: OutputsChanged"
+          echo "desk-autoswitch: outputs changed [$seen]"
           "$DESK" match --apply || true
         fi
         ;;

scripts/desk.sh

@@ -61,7 +61,7 @@ requires() {
 
 notify() {
   # shellcheck disable=SC2086  # word splitting of the prefix is intended
-  $NOTIFY "Desk" "$1" 2>/dev/null || true
+  $NOTIFY "Desk" "$1" >/dev/null 2>/dev/null || true
 }
 
 # Apply a profile: relink, validate live config, roll back on failure,