fix: ci(cedarling): sign auto-generated benchmark commits + add provenance/units -autocreated

This issue was created because no open issues were referenced in your PR (#14816).

Start with pull request #14816 and inspect the Cedarling CI configuration and benchmark commit generation path. Confirm that automatically generated benchmark commits are signed and include provenance and units, then use the pull request checks to verify the completed workflow.

Written by the indexing model from the issue text.