Fixes WCAG 2.1 AA contrast failure (#341): text-accent (#a1dcd8) on light
PDF control bar was 1.52:1 — well below the 4.5:1 AA minimum. text-primary
resolves to #012851 in light mode (14.5:1) and #a1dcd8 in dark mode (9:1) —
both states pass AA in both themes.
Adds PdfControls.svelte.spec.ts with 5 tests covering toggle visibility,
label strings, and the contrast-safe class assertion.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
