home: zsh: add 'zsh-completion-sync'

It's gated behind `completionSync.enable`, as it does make
entering/leaving direnv-enabled projects slower (due to the calls to
`compinit`).

This might need a bit more work to avoid multiple `compinit`s at shell
startup, will refine in the future if necessary.

flake.lock

@@ -159,11 +159,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1760969583,
-        "narHash": "sha256-vsf5mvR0xxK4GsfLx5bMJAQ4ysdrKymMIifNw+4TP7g=",
+        "lastModified": 1761530345,
+        "narHash": "sha256-+9+YCK9Lh6GThkXu/8JTxMFUnImIdZpb8ElUh6/F5Y8=",
         "owner": "nix-community",
         "repo": "home-manager",
-        "rev": "c9d758b500e53db5b74aa02d17dc45b65229e8e9",
+        "rev": "bbaeb9f1c29e79bb1653b32c3d73244cdf4bd888",
         "type": "github"
       },
       "original": {
@@ -175,11 +175,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1760878510,
-        "narHash": "sha256-K5Osef2qexezUfs0alLvZ7nQFTGS9DL2oTVsIXsqLgs=",
+        "lastModified": 1761373498,
+        "narHash": "sha256-Q/uhWNvd7V7k1H1ZPMy/vkx3F8C13ZcdrKjO7Jv7v0c=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "5e2a59a5b1a82f89f2c7e598302a9cacebb72a67",
+        "rev": "6a08e6bb4e46ff7fcbb53d409b253f6bad8a28ce",
         "type": "github"
       },
       "original": {

modules/home/zsh/default.nix

@@ -8,6 +8,10 @@ in
 
     launchTmux = mkEnableOption "auto launch tmux at shell start";
 
+    completionSync = {
+      enable = mkEnableOption "zsh-completion-sync plugin";
+    };
+
     notify = {
       enable = mkEnableOption "zsh-done notification";
 
@@ -118,6 +122,18 @@ in
       };
     }
 
+    (lib.mkIf cfg.completionSync.enable {
+      programs.zsh = {
+        plugins = [
+          {
+            name = "zsh-completion-sync";
+            file = "share/zsh-completion-sync/zsh-completion-sync.plugin.zsh";
+            src = pkgs.zsh-completion-sync;
+          }
+        ];
+      };
+    })
+
     (lib.mkIf cfg.notify.enable {
       programs.zsh = {
         plugins = [