BLAST Results — Empty-Column Reason Banner (#32)

Motivation

When a BLAST search uses -outfmt 7 std staxids sscinames (the dashboard's "Mode B core_nt tabular + taxids" path), the result table's Description and HSP Cover columns are necessarily blank, because that specifier carries no source data:

• Description renders stitle (subject title) — not in std or the taxonomy columns.
• HSP Cover renders qcovs, which the backend derives from qlen (query length) — std carries no qlen.

This is correct given the chosen outfmt, but the columns were present yet always empty with no explanation. NCBI Web BLAST always shows Description + Query Cover, so a researcher reasonably reads the blanks as missing data.

User-facing change

When every hit in the result set has no stitle (Description) and/or no derivable qcovs (HSP Cover), the results table renders a one-line note above the table:

Description and HSP Cover are blank for this run. This search used a tabular output format (e.g. 7 std staxids sscinames) that does not include stitle (Description) or qlen (needed for HSP Cover). Re-run with stitle qlen appended to the outfmt specifier, or use outfmt 5 (XML), to populate these columns.

The banner only shows when the whole result set is blank for that column, so a genuinely populated run (e.g. outfmt 5 XML, which always carries both) never sees it.

API / IaC diff summary

Frontend-only, presentational:

• web/src/pages/blastResults/analytics/BlastHitsTable.tsx — compute descriptionColumnEmpty / coverColumnEmpty from the hit set and render a role="note" banner when either is whole-set blank.

No backend, schema, or outfmt change. (Changing the default preset outfmt was considered — option 1 in the issue — but is deferred so we do not silently widen every taxonomy run's column set.)

Validation evidence

• cd web && npm run build → success.
• npx vitest related --run …BlastHitsTable.tsx → 87 passed (incl. existing BlastHitsTable.test.ts).