fix(renderer): auto-bind ScrollBox wheel input

[re-marked]

Summary

• auto-scroll the nearest <ScrollBox> under the mouse wheel cursor using the existing hit-test/z-order model
• preserve legacy useInput wheel events by attaching parsed mouse coordinates instead of swallowing wheel keypresses
• add wheelStep and disableWheel props, subscriber notification for wheel scrolls, and docs for nested/double-scroll behavior

Verification

• pnpm test -- packages/renderer/src/events/mouse-event.test.ts packages/renderer/src/parse-keypress.test.ts packages/renderer/src/components/ScrollBox.test.tsx
• pnpm --filter @yokai-tui/renderer typecheck
• pnpm --filter @yokai-tui/renderer lint
• pnpm --filter @yokai-tui/renderer build
• pnpm test
• git diff --check

Closes #62