chore(lib): add "auto generated" comment to nix generator outputs

fix copy not being able to overwrite generated files due to them being
read only (r--r--r--) by removing them first

lib/lib.nix

@@ -14,8 +14,26 @@
       format = opts.format or "json";
       formatOpts = builtins.removeAttrs opts ["format"];
       formatter = formats.${format} formatOpts;
+
+      autogeneratedMessage =
+        {
+          yaml = "# Generated by soonix, DO NOT EDIT";
+          toml = "# Generated by soonix, DO NOT EDIT";
+          lua = "--- Generated by soonix, DO NOT EDIT";
+          xml = "<!-- Generated by soonix, DO NOT EDIT -->";
+        }.${
+          format
+        } or "";
     in
-      formatter.generate name data;
+      (formatter.generate name data).overrideAttrs (pre: {
+        buildCommand =
+          # sh
+          ''
+            ${pre.buildCommand}
+            cp $out tmp
+            cat <(echo "${autogeneratedMessage}") tmp > $out
+          '';
+      });
 
     string = {
       name,

lib/module.nix

@@ -133,6 +133,8 @@ in {
             if [[ ! -f "${hook.output}" ]] || ! cmp -s "${hook.generatedDerivation}" "${hook.output}"; then
               _soonix_log "info" "${hookName}" "Copying file: ${hook.generatedDerivation} -> ${hook.output}"
               mkdir -p "$(dirname "${hook.output}")"
+              # required since they're read only
+              rm -f "${hook.output}"
               cp "${hook.generatedDerivation}" "${hook.output}"
               _changed=true
             else