fix(ci): add ESLint config and fix Bundler version compatibility

- Add .eslintrc.json for VSCode plugin ESLint v8 compatibility
- Downgrade Bundler from 2.7.2 to 2.5.23 to support Ruby 3.0/3.1

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: yhk1038

Gemfile.lock

@@ -88,4 +88,4 @@ DEPENDENCIES
   t-ruby!
 
 BUNDLED WITH
-   2.7.2
+   2.5.23

editors/vscode/.eslintrc.json

@@ -0,0 +1,28 @@
+{
+  "root": true,
+  "parser": "@typescript-eslint/parser",
+  "parserOptions": {
+    "ecmaVersion": 2020,
+    "sourceType": "module"
+  },
+  "plugins": [
+    "@typescript-eslint"
+  ],
+  "extends": [
+    "eslint:recommended",
+    "plugin:@typescript-eslint/recommended"
+  ],
+  "rules": {
+    "@typescript-eslint/naming-convention": "off",
+    "@typescript-eslint/semi": "warn",
+    "curly": "warn",
+    "eqeqeq": "warn",
+    "no-throw-literal": "warn",
+    "semi": "off"
+  },
+  "ignorePatterns": [
+    "out",
+    "dist",
+    "**/*.d.ts"
+  ]
+}