Fix isSectionEmpty to ignore Jira reference links and previous footer

[gobetti]

Summary

• Testing Done not filled: Jira's GitHub integration appends reference-style link definitions ([IM-2611]: https://...) to the PR body. Since Testing Done is the last section, the isSectionEmpty regex captures to end-of-string and picks up this link as content, making the section appear non-empty. Fixed by stripping reference-style links, HTML comments, horizontal rules, and our own previous footer text before checking emptiness — so only genuine user-written content counts.
• Footer --- dropped by GitHub: GitHub silently drops --- from PR bodies when it follows an HTML comment in certain contexts. Switched to *** which renders identically as a horizontal rule but survives GitHub's body processing.
• Retry after partial fill: Previously, if Testing Done got a footer but no actual suggestions (e.g. Claude API timed out), subsequent runs would see the footer text and skip the section forever. The new stripping logic treats previous footers as noise, allowing the section to be retried.

Test plan

• Open a PR where Jira adds a reference link before the workflow runs — Testing Done should still be filled
• Re-run the workflow on a PR where Testing Done only has a placeholder + footer — it should attempt to fill the suggestions again
• Verify the *** separator renders as a horizontal rule in the PR body

🤖 Generated with Claude Code

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📝 Auto-filled