test: Enhance claim-handler test coverage and edge case validation

[ANSHIKATYAGI30]

Description

This PR enhances the test suite for the issue claim handler by improving coverage and validating additional edge cases.

Changes Made-:

Issue 1 – Improve Test Coverage

• Added missing test cases for previously uncovered claim-handler scenarios.
• Improved validation of different issue ownership conditions.
• Verified correct assignment behavior across multiple claim paths.
• Increased overall reliability of the claim workflow.

Issue 2 – Add Missing Edge Case Validation

• Added a dedicated test for handling issues with multiple existing assignees.
• Ensured the handler rejects new claims when an issue is already assigned.
• Verified the correct rejection message is returned.
• Improved robustness against invalid claim attempts.

Fixes #8427

Checklist before requesting a review:

• I have read the CONTRIBUTING.md file.
• I have tested these changes locally (localhost:3000/api/streak?user=YOUR_USERNAME).
• I have run npm run format and npm run lint locally and resolved all errors (CI will fail otherwise).
• My commits follow the Conventional Commits format (e.g., feat(themes): ..., fix(calculate): ...).
• I have updated README.md if I added a new theme or URL parameter.
• I have made sure that i have only one commit to merge in this PR.
• The SVG output matches the CommitPulse "premium quality" aesthetic standard (no raw elements, smooth animations, correct fonts).
• (Recommended) I joined the CommitPulse Discord community for contributor discussions, mentorship, and faster PR support.

[vercel]

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[retenta-bot]

This pull request significantly enhances the test coverage for the claim handler, which is crucial for maintaining the reliability of the claim workflow. It also addresses edge cases that could lead to unexpected behavior. This approach aligns with our previous decisions to improve error resilience and exception handling in other components, such as the AdvancedSettingsPanel and utility functions. Great work on ensuring comprehensive testing! Looking forward to your next contributions!

[github-actions]

🚨 Hey @ANSHIKATYAGI30, the CI Pipeline is failing on this PR and it has been marked as status:blocked.

Please fix the issues before this can be reviewed. Here's how:

1. Run checks locally before pushing:

npm run format:check   # Check Prettier formatting
npm run lint           # Run ESLint
npm run typecheck      # TypeScript type check
npm run test           # Run unit tests (Vitest)
npm run build          # Verify production build passes

2. Auto-fix common issues:

npm run format         # Auto-fix formatting with Prettier
npm run lint -- --fix  # Auto-fix lint errors where possible

3. Check the full failure log here:
👉 View CI Run

Once you push a fix and the CI passes, the status:blocked label will be removed automatically. 💪