Address the review comments on the subprocessors work:
- Reject invalid category/country filter values in the Subprocessors
resolver with an INVALID error instead of relying solely on transport
coercion, so a malformed request fails fast and explicitly.
- Use pgx.StrictNamedArgs in the new distinct facet queries so missing
or extra SQL placeholders stay detectable, matching sibling queries.
- Default a nil ThirdPartyFilter at the service boundary to avoid a nil
dereference in the coredata list/count paths.
- Expose the category group label as an aria heading for assistive tech.
- Add the missing space in the Select "Selected:" story label.
Signed-off-by: Émile Ré <emile@probo.com>
c7c05f0e8d