feat(issues): Warn about similar open issues during issue generation

[thomas-vilte]

Description

I implemented a new feature that warns users about potentially similar open issues when generating a new issue. After an issue title is generated, the system now performs a lightweight keyword-overlap comparison against currently open issues in the repository. If a significant overlap (at least 2 shared words and 50% similarity ratio) is found, a warning message is displayed, listing the similar open issues with their numbers, titles, and URLs. This helps prevent the creation of duplicate issues.

The IssueGeneratorService now includes a FindSimilarOpenIssues method, which utilizes a new ListOpenIssues method in the VCSClient interface and its GitHub implementation. The similarity check uses a significantWords helper to tokenize and filter common words from issue titles.

Fixes #

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

How Has This Been Tested?

I added unit tests for the FindSimilarOpenIssues method in internal/services/issue_generator_service_test.go to cover various scenarios of similarity detection and error handling.
I also updated internal/commands/issues/issues_test.go to mock the new FindSimilarOpenIssues call during issue generation.

• Unit tests
• Integration tests
• Manual test: (describe below)

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Test Plan & Evidence

Suggested Manual Verification

• API/Backend: Attach JSON response or logs as evidence of correct behavior
• Performance: Ensure no significant latency increase
• Unit Tests: Run go test ./... and ensure all tests pass
• No Regressions: Verify that related features still work as expected