fix: ignore stationary palette mouse hover

[cat0825]

Replacement for accidentally closed #830.

Fixes #819.

Summary

• Ignore zero-delta/stationary mousemove events in command palette and quick-open result lists.
• Allow mouse hover selection only after the cursor position actually changes.
• Add regression coverage for keyboard selection staying stable after palette open and after keyboard navigation reclaims selection.

Verification

• pnpm test src/utils/mouseMovement.test.ts src/components/NoteSearchList.test.tsx src/components/QuickOpenPalette.test.tsx src/components/CommandPalette.test.tsx
• npx tsc --noEmit
• pnpm lint
• Full pre-push rerun progressed through lint, build, frontend coverage, and Rust lint; first attempt stopped at missing local cargo-llvm-cov before the tool was installed.