drop snixembed: waybar provides its own SNI watcher

snixembed registered as the StatusNotifierWatcher but its
RegisterStatusNotifierItem implementation didn't accept SNI publishers
— Telegram, Vesktop, blueman-tray, and a libayatana-appindicator test
script all failed to register, leaving waybar's tray empty.

Removing snixembed lets waybar's tray module register itself as both
host AND watcher (when no other watcher exists). After this change,
all three SNI items registered immediately.

Trade-off: legacy XEmbed-based Wine tray icons no longer bridge to
SNI. The Wine System Tray host window rule is kept (still hides the
empty window off-screen) and the comment updated.

- niri/config.kdl: drop snixembed spawn-at-startup; update Wine rule
- packages.txt: drop snixembed (no longer used)

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

niri/config.kdl

@@ -44,7 +44,6 @@ spawn-at-startup "swayidle" "-w" "timeout" "300" "niri msg action power-off-moni
 spawn-at-startup "wl-paste" "--watch" "cliphist" "store"
 spawn-at-startup "wlsunset" "-l" "49.2" "-L" "-123.1"
 spawn-at-startup "xwayland-satellite"
-spawn-at-startup "snixembed" "--no-startup-id"
 
 binds {
     Mod+Q repeat=false { close-window; }
@@ -126,7 +125,7 @@ window-rule {
     variable-refresh-rate true
 }
 
-// Wine System Tray: hide the host window, icons bridge to SNI via snixembed
+// Wine System Tray: hide the empty host window off-screen
 window-rule {
     match app-id="^explorer.exe$"
     match title="^Wine System Tray$"

packages.txt

@@ -12,7 +12,6 @@ brightnessctl
 pamixer
 gtklock
 swayidle
-snixembed
 ttf-jetbrains-mono-nerd
 polkit-gnome
 xdg-desktop-portal-wlr