Mocking upgrade

[TomasKorbar]

• Extract mock repo setup from e2e tests into a shared ymir/common/mock_repos.py module so the same mocking infrastructure can be reused for all mocking
• Add RunShellCommandTool URL blocking via MOCK_BLOCKED_URLS to prevent agents from bypassing mocked repos with curl/wget, replacing the previous shell wrapper approach
• Add scripts/run-mock-triage.py launcher and claude-triage-mock.md guide for running the triage skill against mocked JIRA data locally

[gemini-code-assist]

Code Review

This pull request introduces a comprehensive mocking framework for the triage skill, allowing local execution against mocked JIRA data and CentOS Stream repositories. Key additions include a new utility module for repo fixtures, a launcher script for Claude Code, and updated documentation. Feedback focuses on ensuring proper cleanup of temporary files and directories, specifically addressing the use of os.execvp which bypasses atexit handlers and the lack of deletion for temporary mock repository directories.