feat(workflow): add workflow to unassign inactive issue assignees

[Harxhit]

Auto-unassign issues without linked PRs

Summary

Adds a scheduled GitHub Actions workflow that automatically checks assigned open issues and unassigns them if no linked pull request is found.

The workflow runs every 5 days and can also be triggered manually using workflow_dispatch. If an assigned issue does not have a linked open PR, the workflow:

• Removes all assignees
• Posts an automated notification comment
• Informs contributors how to retain assignment by opening and linking a PR

This helps keep issue assignments active, prevents stale ownership, and improves repository maintenance.

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Type of Change

• Bug fix
• New feature
• Refactor (no functional change)
• UI / Design change
• Tests only
• Documentation
• Infrastructure / DevOps
• Security

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What Changed

• Added a new GitHub Actions workflow to detect assigned issues without linked PRs
• Configured the workflow to run automatically every 5 days via cron schedule
• Added workflow_dispatch support for manual execution
• Implemented timeline event checks to detect linked open pull requests
• Automatically removes assignees from issues that do not have linked PRs
• Added automated notification comments explaining the unassignment
• Included workflow permissions for issue write access
• Added support for repository authentication using GITHUB_TOKEN

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Workflow Configuration

This workflow requires the GitHub token to authenticate API requests:

github-token: ${{ secrets.GITHUB_TOKEN }}

The token is used for:

• Reading issue timeline events
• Checking linked pull requests
• Removing assignees
• Posting automated comments

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How to Test

1. Assign a user to an open issue
2. Leave the issue without any linked pull request
3. Trigger the workflow manually using workflow_dispatch or wait for the scheduled run
4. Verify that:
   • The assignee is removed
   • An automated notification comment is posted
5. Create a linked PR for another issue and verify that the assignment remains unchanged

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Checklist

• My code follows the project's coding style (pnpm -r run lint passes).
• TypeScript compiles without errors (pnpm -r run typecheck).
• I have added or updated tests for the changes I made.
• All tests pass locally (pnpm -r run test).
• I have updated documentation where necessary.
• No new console.log or debug statements left in the code.
• Breaking changes are documented in this PR description.

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Additional Context

The workflow relies on GitHub issue timeline events to identify cross-referenced pull requests. Issues with linked open PRs are preserved, while stale assignments without linked work are automatically cleaned up.