Update sort logic for court case index page

[patphongs]

Summary

During migration of court case information from the current alphabetical index to the new programmatically generated index, a question arose regarding the ordering of cases with identical names.

On the current alphabetical index, when multiple cases share the same name, they are displayed in chronological order (oldest to newest). For example, the Campaign Legal Center cases are currently listed as:

• Campaign Legal Center v. FEC (21-1376)
• Campaign Legal Center v. FEC (22-838)
• Campaign Legal Center v. FEC (22-1976 / 22-5339) — ongoing litigation

The new index page currently displays these cases in reverse chronological order, reflecting the sorting logic used for the “Ongoing litigation” and "Selected court cases" lists on the court cases landing page. We will maintain this order.

The goal now is to ensure the sort uses the first court case number in the page title for its reverse chronological index. The higher the number, the more recent the case. Like this:

• Campaign Legal Center v. FEC (22-1976 / 22-5339) — ongoing litigation
• Campaign Legal Center v. FEC (22-838)
• Campaign Legal Center v. FEC (21-1376)

Completion criteria

• Cases with identical names on the alphabetical court case index are displayed in reverse chronological order (newest to oldest). The high court case number is shown first in the list as it is the most recent.
• Reverse chronological sorting is maintained throughout for the alphabetical index, active, and selected court cases list.