fix: prevent token mutation (#71)

* fix: prevent token mutation

* fix: accept readonly array in concatJoishiTokens function

Fixed TypeScript compilation error where concatJoishiTokens was expecting
a mutable array but received a readonly array from the tokenize function.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

---------

Co-authored-by: azu <[email protected]>
Co-authored-by: Claude <[email protected]>

Author: 3 people

src/no-doubled-joshi.ts

@@ -275,7 +275,7 @@ const report: TextlintRuleModule<Options> = function (context, options = {}) {
                     }
                     // strict mode ではない時例外を除去する
                     if (!isStrict) {
-                        if (matchExceptionRule(joshiTokenSurfaceTokens, tokens)) {
+                        if (matchExceptionRule(joshiTokenSurfaceTokens, concatedJoshiTokens)) {
                             return;
                         }
                     }
@@ -292,11 +292,11 @@ const report: TextlintRuleModule<Options> = function (context, options = {}) {
                         if (differenceIndex <= minInterval) {
                             // 連続する助詞を集める
                             const startWord = toTextWithPrevWord(prev, {
-                                tokens: tokens,
+                                tokens: concatedJoshiTokens,
                                 sentence: sentence
                             });
                             const endWord = toTextWithPrevWord(current, {
-                                tokens: tokens,
+                                tokens: concatedJoshiTokens,
                                 sentence: sentence
                             });
                             // padding positionを計算する

src/token-utils.ts

@@ -36,17 +36,19 @@ export const create読点Matcher = (commaCharacters: string[]) => {
  * @returns {Object}
  */
 const concatToken = (aToken: KuromojiToken, bToken: KuromojiToken) => {
-    aToken.surface_form += bToken.surface_form;
-    aToken.pos += bToken.pos;
-    aToken.pos_detail_1 += bToken.surface_form;
-    return aToken;
+    return {
+        ...aToken,
+        surface_form: aToken.surface_form + bToken.surface_form,
+        pos: aToken.pos + bToken.pos,
+        pos_detail_1: aToken.pos_detail_1 + bToken.surface_form
+    };
 };
 /**
  * 助詞+助詞 というように連続しているtokenを結合し直したtokenの配列を返す
  * @param {Array} tokens
  * @returns {Array}
  */
-export const concatJoishiTokens = (tokens: KuromojiToken[]) => {
+export const concatJoishiTokens = (tokens: readonly KuromojiToken[]) => {
     const newTokens: KuromojiToken[] = [];
     tokens.forEach((token) => {
         const prevToken = newTokens[newTokens.length - 1];