Adopt PRIDE spore-coat proteomics dataset PXD004473

[realmarcin]

Goal

Adopt PRIDE Archive as a lightweight proteomics-dataset source, beginning with
the exact spore-coat dataset PXD004473 on the endospore record.

This closes a real corpus gap: only 4 of 19 records currently have a datasets
entry, while PROTEOMICS and PRIDE are already supported schema values.

Verified canary

The official PRIDE v2 project endpoint for PXD004473 currently returns:

• title: The influence of sporulation medium on the spore coat protein
  composition of Bacillus subtilis spores.
• organism: NEWT:135461, Bacillus subtilis subsp. subtilis
• publication date: 2017-09-20
• PMID: 27790212
• submission type: PARTIAL

Research and primary links are recorded in
research/2026-09-02-next-data-sources.md.

Adapter boundary

• Resolve an exact PXD accession through the official project API; do not
  select the first keyword-search result.
• Validate exact title, organism, publication, submission type, and PMID for the
  fixed canary.
• Add a lightweight PROTEOMICS / PRIDE dataset reference and source URL;
  do not download or commit raw mass-spectrometry files.
• Do not promote every protein identification to a structural component. That
  requires paper-specific interpretation and curator review.
• Keep the queue's identifier-only REFERENCE boundary unless the repository
  gains a more precise representation of EMBL-EBI Terms of Use.

Acceptance criteria

• deterministic adapter with dry-run default and explicit apply mode
• exact live or fixture-backed PXD004473 contract tests
• one dataset entry on the endospore record with accession, repository,
  type, publication, and URL
• source configuration and queue row become ADOPTED
• just qc passes