fix(cron): preserve pause when a running job finishes

[lewismosciski]

Change Summary

Pausing a running recurring job currently lasts only until that run finishes: record_result() changes its status back to scheduled. Preserve paused while recording the result and advancing the next run. One-shot jobs and exhausted repeat limits still complete normally.

Added regressions for successful/failed runs, terminal states, and a background run paused through a separate manager sharing the jobs file.

Validation: python -m pytest tests/cron -q (103 passed); pre-commit passed for all three changed files. Full-repo pre-commit still reports existing failures on unchanged main, including ms_agent/config/skills_manager.py:61 and ms_agent/permission/shell_validator.py:91.

Related issue number

None; found while tracing cron state transitions.

Checklist

• The pull request title is a good summary of the changes - it will be used in the changelog
• Unit tests for the changes exist
• Run pre-commit install and pre-commit run --all-files before git commit, and passed lint check. Ran both; full-repo failures noted above.
• Documentation reflects the changes where applicable (no command or configuration changes)