refactor: unify Walker configuration into Nix and delete legacy TOML

modules/home/walker.nix

@@ -11,6 +11,32 @@
           top = true;
         };
       };
+      selection_wrap = true;
+      hide_action_hints = true;
+      placeholders = {
+        "default" = { input = " Search..."; list = "No Results"; };
+      };
+      keybinds = {
+        quick_activate = [];
+      };
+      columns = {
+        symbols = 1;
+      };
+      providers = {
+        max_results = 256;
+        default = [
+          "desktopapplications"
+          "websearch"
+        ];
+        prefixes = [
+          { prefix = "/"; provider = "providerlist"; }
+          { prefix = "."; provider = "files"; }
+          { prefix = ":"; provider = "symbols"; }
+          { prefix = "="; provider = "calc"; }
+          { prefix = "@"; provider = "websearch"; }
+          { prefix = "$"; provider = "clipboard"; }
+        ];
+      };
     };
     themes."nomarchy" = {
       style = ''