Search: Ability to group results by a specific field

When the number of results is under a specific threshold (e.g. 500 results):

- display all results on the page (get rid of pagination)
- allow the user to "group by" a specific column
- rows will be grouped by that column in buckets on the page

This would enable the computation of aggregated metrics on numeric columns, or histograms for categorical data, similar to what Airtable does.

Start by locating the search results page and its pagination behavior in the Nexus codebase. Review how result columns and numeric or categorical values are represented, then determine how the proposed threshold, grouping buckets, and aggregated metrics or histograms should work. Done means small result sets can be displayed without pagination and grouped by a selected field.

Written by the indexing model from the issue text.