plugins/utility/fff-nvim: add fff.nvim module

Adds fff.nvim, a high-performance Rust-backed file picker for Neovim
with fuzzy search and frecency scoring. The Rust shared library is
built from source via rustPlatform.buildRustPackage and symlinked into
target/release/ where the plugin's lua loader expects it.

Toggle with vim.utility.fff-nvim.enable; pass arbitrary fff.setup()
options through vim.utility.fff-nvim.setupOpts.

modules/plugins/utility/default.nix

@@ -4,6 +4,7 @@
     ./ccc
     ./diffview
     ./direnv
+    ./fff-nvim
     ./fzf-lua
     ./gestures
     ./harpoon

modules/plugins/utility/fff-nvim/config.nix

@@ -0,0 +1,25 @@
+{
+  config,
+  lib,
+  ...
+}: let
+  inherit (lib.modules) mkIf;
+
+  cfg = config.vim.utility.fff-nvim;
+in {
+  vim.lazy.plugins."fff-nvim" = mkIf cfg.enable {
+    package = "fff-nvim";
+    setupModule = "fff";
+    inherit (cfg) setupOpts;
+
+    cmd = [
+      "FFFFind"
+      "FFFScan"
+      "FFFRefreshGit"
+      "FFFClearCache"
+      "FFFHealth"
+      "FFFDebug"
+      "FFFOpenLog"
+    ];
+  };
+}

modules/plugins/utility/fff-nvim/default.nix

@@ -0,0 +1,6 @@
+{
+  imports = [
+    ./fff-nvim.nix
+    ./config.nix
+  ];
+}

modules/plugins/utility/fff-nvim/fff-nvim.nix

@@ -0,0 +1,80 @@
+{
+  lib,
+  ...
+}: let
+  inherit (lib.options) mkEnableOption mkOption;
+  inherit (lib.types) attrs;
+  inherit (lib.nvim.types) mkPluginSetupOption;
+in {
+  options.vim.utility.fff-nvim = {
+    enable = mkEnableOption "fff.nvim, a fast file picker for Neovim";
+
+    setupOpts = mkPluginSetupOption "fff.nvim" {
+      base_path = mkOption {
+        type = lib.types.nullOr lib.types.str;
+        default = null;
+        description = "Base directory for searching files. Defaults to the current working directory.";
+      };
+
+      prompt = mkOption {
+        type = lib.types.str;
+        default = "  ";
+        description = "Prompt symbol used by the picker.";
+      };
+
+      title = mkOption {
+        type = lib.types.str;
+        default = "FFF Files";
+        description = "Title of the picker window.";
+      };
+
+      max_results = mkOption {
+        type = lib.types.int;
+        default = 100;
+        description = "Maximum number of results to display.";
+      };
+
+      max_threads = mkOption {
+        type = lib.types.int;
+        default = 4;
+        description = "Maximum number of background threads used for search.";
+      };
+
+      layout = mkOption {
+        type = attrs;
+        default = {};
+        description = "Layout settings (height, width, prompt_position, preview_position, ...).";
+      };
+
+      preview = mkOption {
+        type = attrs;
+        default = {};
+        description = "Preview settings (enabled, max_size, line_numbers, ...).";
+      };
+
+      keymaps = mkOption {
+        type = attrs;
+        default = {};
+        description = "Keymap overrides for the picker.";
+      };
+
+      icons = mkOption {
+        type = attrs;
+        default = {};
+        description = "Icon settings (requires a Nerd Font / icon provider).";
+      };
+
+      frecency = mkOption {
+        type = attrs;
+        default = {};
+        description = "Frecency database settings.";
+      };
+
+      debug = mkOption {
+        type = attrs;
+        default = {};
+        description = "Debug-related settings.";
+      };
+    };
+  };
+}