when selecting roomy messages the checkbox doesn't check #144

Fixed Roomy message selection so checkbox clicks retain the browser's native checked state while continuing to update Radial's plain and shift-range selection model.

Added component regression coverage that verifies the visible checkbox states after selecting one message and a shifted range.

Checks:

• pnpm --filter @radial/ui exec vitest run --project components src/lib/components/RoomyThread.svelte.test.ts
• pnpm lint
• pnpm test

Radial artifact