MIGRATION: Handle Jira auto-numbered ordered list syntax

[This sample issue](https://github.com/toddfarmer/test_import/issues/268) demonstrates a gap in the jira2markdown syntax conversion utility, which apparently does not recognize Jira's auto-numbered ordered list syntax. This results in it being left as-is, which then renders as markdown headers instead. This probably needs to be fixed before migration.

Start with the jira2markdown syntax conversion utility and compare its behavior with the linked sample issue. Update the conversion so Jira auto-numbered ordered lists become valid Markdown ordered lists rather than headers, then verify the resulting rendered output.

Written by the indexing model from the issue text.