Document Galaxy list-of-record collections for reference data

Surfaced from the [reference-data Mold revision](https://github.com/jmchilton/foundry/pull/224) — `content/research/nextflow-to-galaxy-reference-data-mapping.md` lists "list of records" as a Galaxy-side option for reference data alongside `sample_sheet`-shaped collections, but there is no research note on it yet to wiki-link.

## What we want

A research note (likely `content/research/galaxy-list-record-collections.md` or similar) covering Galaxy's `list:record` / record-shaped collection types:

- Collection-type vocabulary in `lib/galaxy/model/dataset_collections/types/`.
- How `record` differs from `sample_sheet` semantically — the framing in the reference-data note is that `sample_sheet` forces a unique element identifier per row, whereas a list of records can carry column-like metadata without that uniqueness restriction.
- Tool-wrapper input shapes that consume these.
- Reference-data-shaped use cases vs sample-data-shaped use cases.

## Where it gets cited

Once written, link from `content/research/nextflow-to-galaxy-reference-data-mapping.md` (currently has prose noting this is a future research peer) and from `content/research/galaxy-sample-sheet-collections.md` for cross-reference.

## Out of scope

- Authoring the actual collection-type translation rules from Nextflow — that lives in the existing `nextflow-to-galaxy-channel-shape-mapping` and `galaxy-sample-sheet-collections` notes; this issue is just the missing peer reference page.