Remove Gemfile.lock from repository

- Add Gemfile.lock to .gitignore
- Remove explicit Gemfile.lock deletion step from ci.yml
- Gemfile.lock should not be committed for gems as it causes
  dependency conflicts across different Ruby versions

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

Author: koji-takao-sp

.github/workflows/ci.yml

@@ -20,8 +20,6 @@ jobs:
 
     steps:
     - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
-    - name: Remove Gemfile.lock for fresh dependency resolution
-      run: rm -f Gemfile.lock
     - name: Set up Ruby
       uses: ruby/setup-ruby@90be1154f987f4dc0fe0dd0feedac9e473aa4ba8 # v1.286.0
       with:

.gitignore

@@ -8,3 +8,4 @@
 /tmp/
 /test/fixtures/late-dep/empty.js
 node_modules
+Gemfile.lock