Improve Generate-query modal readability (WCAG AA)¶

Motivation¶

The New Search Generate query from NCBI modal (SequenceBuilderDialog) had three accessibility/readability defects:

The unselected strand toggle (Plus / Minus) was dimmed with opacity: 0.5. Opacity dimming drops the effective text contrast below WCAG AA and conveys the selected state by colour/brightness alone.
The NCBI search-result rows and gene-feature rows used hardcoded rgba(255,255,255,0.04) backgrounds (and rgba(120,170,255,0.12) for the selected row). These are dark-theme-only: on the light theme's solid-white panels they render as near-invisible rows, losing the card affordance.

The strand toggle now keeps both labels at full, AA-compliant contrast: the unselected button uses --text-muted (≈5.4:1 dark / ≈7:1 light) and the selected one is shown with a filled background, focus-coloured border, and bold weight — plus aria-pressed so screen readers get the state, not just a colour cue.
The search-result and feature rows now use the theme-aware --bg-tertiary surface, with the selected accession row tinted via color-mix(in srgb, var(--accent) 16%, var(--bg-tertiary)) and a --border-focus outline, so the rows are clearly visible in both light and dark themes. Selected rows also expose aria-pressed.

No behaviour change — only styling and ARIA state.

Frontend only: web/src/pages/blastSubmit/SequenceBuilderDialog.tsx. No backend, no API, no IaC change.

npx eslint src/pages/blastSubmit/SequenceBuilderDialog.tsx — clean.
npx vitest run src/pages/blastSubmit/SequenceBuilderDialog.test.ts — 14 passed (pure helpers unaffected).
npm run build — succeeds.
Contrast: unselected toggle --text-muted on --bg-primary/white meets AA (≥4.5:1) in both themes; previously the 50%-opacity label fell well below AA.