[REQUEST] Show relationship-field changes when selecting a changed diff row

Is your feature request related to a problem? Please describe.
The diff modal highlights changed relationship rows, such as Procedure Examples or Mitigations, but selecting a changed row does not always show what changed. For example, an updated URL in a relationship reference/citation is not displayed as a specific change.

Describe the solution you'd like
When a user selects a highlighted relationship row, show field-level differences for that relationship object, including changes to references, citations, and citation URLs.

Describe alternatives you've considered
Reviewers can compare the source and target objects outside the diff modal, but this is slow and makes relationship-level changes difficult to verify.

Additional context
This should work consistently for relationship-based tabs, including Procedure Examples and Mitigations, and should clearly distinguish added, removed, and modified field values.

Start at the diff modal's relationship-row selection flow and trace how changed rows are rendered for Procedure Examples and Mitigations. Verify the result against relationship objects containing references, citations, and citation URLs; done means selected rows clearly show added, removed, and modified field values consistently across both tabs.