chore(niri): remove pyclipsync clipboard bridge

WeChat and QQ now use native Wayland, so the X11/Wayland clipboard bridge
is no longer needed. Remove the flake input, home-manager module wiring,
lock entries, and stale documentation reference.

Assisted-by: DeepSeek Harness (deepseek-flash)

home/linux/gui/niri/default.nix

@@ -2,18 +2,12 @@
   pkgs,
   config,
   lib,
-  pyclipsync,
   ...
 }@args:
 let
   cfg = config.modules.desktop.niri;
 in
 {
-  imports = [
-    # provides `services.pyclipsync.enable`
-    pyclipsync.homeModules.default
-  ];
-
   options.modules.desktop.niri = {
     enable = lib.mkEnableOption "niri compositor";
   };
@@ -57,13 +51,6 @@ in
           };
         };
 
-        # xwayland-satellite has no compositor-level clipboard bridging, so X11
-        # clients (WeChat/QQ, run via xwayland-satellite) and Wayland clients
-        # cannot see each other's clipboard. This daemon mirrors the X11
-        # CLIPBOARD and the Wayland data device both directions (see the
-        # pyclipsync repo for details).
-        services.pyclipsync.enable = true;
-
         # NOTE: this executable is used by greetd to start a wayland session when system boot up
         # with such a vendor-no-locking script, we can switch to another wayland compositor without modifying greetd's config in NixOS module
         home.file.".wayland-session" = {