feat(home): add pyclipsync clipboard sync service for niri

xwayland-satellite has no compositor-level clipboard bridging, so X11
clients (WeChat/QQ) and Wayland clients cannot see each other's clipboard.
Add the pyclipsync flake input and enable its home-manager module, which
installs the daemon as a systemd user service bound to the graphical session.

flake.lock

@@ -842,6 +842,26 @@
         "type": "github"
       }
     },
+    "pyclipsync": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1787650021,
+        "narHash": "sha256-rUcNR2oIAVCQA4TJR1jU38cHnd0j9njNZLOj8n2oeHk=",
+        "owner": "ryan4yin",
+        "repo": "pyclipsync",
+        "rev": "2a427d11e8e2195703a8f84a734cad4c68d5875c",
+        "type": "github"
+      },
+      "original": {
+        "owner": "ryan4yin",
+        "repo": "pyclipsync",
+        "type": "github"
+      }
+    },
     "root": {
       "inputs": {
         "agenix": "agenix",
@@ -869,6 +889,7 @@
         "nur-ryan4yin": "nur-ryan4yin",
         "pre-commit-hooks": "pre-commit-hooks",
         "preservation": "preservation",
+        "pyclipsync": "pyclipsync",
         "wallpapers": "wallpapers"
       }
     },

flake.nix

@@ -168,5 +168,11 @@
       url = "github:ryan4yin/nur-packages";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+
+    # Wayland <-> X11 clipboard sync daemon for xwayland-satellite (niri)
+    pyclipsync = {
+      url = "github:ryan4yin/pyclipsync";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 }

home/linux/gui/niri/default.nix

@@ -2,12 +2,18 @@
   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";
   };
@@ -56,6 +62,13 @@ 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" = {