Autocomplete highlight: visible selection color in the CMS

#40 in Riparion/riparion-cms — merged 2026-06-02

Completes the [[/ autocomplete keyboard UX: the selected row is now visibly highlighted in the CMS.

• Bumps the riparion-editor pin to pick up Riparion/riparion-editor#6 — popup items render as a <div> instead of a <button>, so the selected row's background actually paints (previously an inline background:transparent on the button overrode the active class, so keyboard selection was invisible even though navigation worked).
• Sets the selected-row class to a clearly visible brand tint (bg-brand-500/70) instead of the near-invisible bg-white/5 that was identical to the hover state.

Pin: d6372ed → a669cb2. Verified working in the running CMS.

Checks

clippy -D warnings on server (sqlite + postgres) and wasm runs in CI.