Use make test in GitHub Actions workflow

[Copilot]

The GitHub Actions test workflow was manually invoking docker commands instead of using the standardized make test target defined in the Makefile.

Changes:

• Replaced three separate workflow steps (build, test, rubocop) with single make test invocation
• This ensures CI uses the same test command as local development
• make test handles image build, volume mounting, and runs both bundle exec rake test and bundle exec rubocop

Before:

- name: build
  run: make image
- name: test
  run: docker run --rm ruby_language_server rake | tee test.log
- name: rubocop
  run: docker run --rm ruby_language_server rubocop | tee rubocop.log

After:

- name: Run tests
  run: make test

Original prompt

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This section details on the original issue you should resolve

<issue_title>github does not run the tests</issue_title>
<issue_description>github should run the tests on push. make test</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes github does not run the tests #108

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