[WIP] Fix code based on review comments

[Copilot]

• Add unit tests in labels/mod.rs for the 4 new tool groups added in tool_rules.rs:
  • Granular issue update tools (7 tools: update_issue_assignees, update_issue_body, update_issue_labels, update_issue_milestone, update_issue_state, update_issue_title, update_issue_type)
  • Sub-issue management tools (3 tools: add_sub_issue, remove_sub_issue, reprioritize_sub_issue)
  • Granular PR update tools (4 tools: update_pull_request_body, update_pull_request_draft_state, update_pull_request_state, update_pull_request_title)
  • PR review tools (7 tools: add_pull_request_review_comment, create_pull_request_review, delete_pending_pull_request_review, request_pull_request_reviewers, resolve_review_thread, submit_pending_pull_request_review, unresolve_review_thread)
• Run tests to validate