Comparison Feature

I'm preparing a presentation for one of [CivicActions DITAP cohorts](https://civicactions.com/services/ditap) and realized that it would be really neat to be able to select 3-5 ACRs and have a tool that pick out some comparison notes between them.

It would be possible to highlight:
- the date of the ACR (the more recent the more relevant)
- if it was done by a 3rd party (self-authored ACRs often are less legitimate)
- which claim to be in better compliance with Section 508
- If there are links to external documentation (issue queue)

It could include other elements to help non-experts make more informed decisions around the accessibility of the services offered.

This is definitely for a future phase.

The issue names no files, tests, or entry points; start by reviewing the repository's existing ACR comparison behavior and the presentation use case described here. Before implementation, define the selection flow, comparison criteria, and a concrete completion boundary for the future phase.

Written by the indexing model from the issue text.