sysutils/git-backup: not backing up new firewall rules

Important notices

• I have read the contributing guidelines at https://github.com/opnsense/core/blob/master/CONTRIBUTING.md
• I am convinced that my issue is new after having checked both open and closed issues at https://github.com/opnsense/core/issues?q=is%3Aissue

Describe the bug

I just migrated legacy firewall rules to the new rules.
Git backup didn't produce a commit.
Clicking "Setup/Test Git" produced a new commit, but didn't include new rules and didn't remove legacy rules.

The commit diff only contains

<backup><git persisted_at="<new timestamp>">

<revision>
  <description>/diag_backup.php made changes</description>
  <time><changed timestamp></time>

To Reproduce

Steps to reproduce the behavior:

1. migrate legacy firewall rules
2. click "Setup/Test Git" in System > Configuration > Backups
3. check backup

Expected behavior

Configuration changes should invoke Git backup and Git backup should include the changes

Additional context

This issue could be related to #10289

Git backup worked flawlessy before. The last backup commit was 17h ago.
I updated OPNSense to 26.1.8. Before it was the latest version available yesterday.

When I diff backup files created with "Download configuration" from before and after the rules migration, lots of removal and addition of rules are shown.

Environment

OPNsense 26.1.8 (amd64).

Start with the System > Configuration > Backups “Setup/Test Git” entry point and the /diag_backup.php change noted in the issue. Reproduce the legacy-rule migration, compare configuration backups before and after it, and verify that the Git commit includes the new rules and removes the legacy rules rather than only updating the timestamp.