DP-3630 Give dark-theme prev/next hyperlinks a distinct ink from active-nav lime

[claude]

Requested via Slack thread

What / why

DP-3630 (https://gooddata.atlassian.net/browse/DP-3630): in dark theme, the prev/next-page hyperlink (.gd-docs-prev-next-pages__link) and the active sidebar-nav state (.gd-docs-menu-page.active ... __link) both used the identical $color-lime-green, so the two affordances ("where I am" vs. "where I can go") were indistinguishable by color alone.

Light theme already keeps these distinct ($color-black for active nav vs. $color-link for the prev/next link) — this only affects the dark-theme override.

Change

assets/scss/dark-theme/prev-next-pages.scss:

• &__link color: $color-lime-green -> $color-ice-blue (the palette's existing "Hyperlinks on dark backgrounds" token — already used by the generic a selector in dark-theme/typography.scss, so this reuses an established, already-vetted brand token rather than introducing a new color).
• hover/focus/active color: $color-white -> $color-alice-blue, matching the hover token generic body links already use in dark theme.
• Underline was already present and is preserved, so the link remains distinguishable without relying on color alone (WCAG 1.4.1).

Active-nav lime (dark-theme/menu.scss) is left untouched, per the ticket's proposed fix direction (keep lime for the active-nav affordance).

Acceptance criteria from the ticket

• Active nav state and inline/prev-next link are visually distinguishable without relying on position (different ink color).
• Link no longer relies on lime; uses $color-ice-blue, the same token already used (and implicitly covered by the prior AA audit) for standard dark-theme hyperlinks — avoids the previously-unsampled lime-link contrast combination entirely rather than needing a fresh contrast measurement.
• Color is not the sole differentiator for the link (pre-existing underline retained).

Test plan

• Visually diff a docs page with prev/next navigation in dark theme (e.g. any multi-page docs section) before/after.
• Confirm active sidebar-nav item still renders in lime, unaffected.
• Confirm light theme is unaffected (no changes made to assets/scss/prev-next-pages.scss).