## Summary
Adds Notion-style resizable panels for the navigation drawer (left
sidebar) and command menu (right panel).
## Behavior
- **Hover** at panel edge → resize cursor appears
- **Click** → collapse/close the panel
- **Drag** → resize the panel (5px movement threshold to distinguish
from click)
## Constraints
| Panel | Min | Max | Default | Collapse Threshold |
|-------|-----|-----|---------|-------------------|
| Navigation Drawer | 180px | 350px | 220px | 150px |
| Command Menu | 320px | 600px | 400px | 250px |
## Performance Optimizations
- **CSS variables** for smooth 60fps resize (no React re-renders during
drag)
- **Table resize observer disabled** during panel resize to prevent
expensive recalculations
- **React.memo wrapper** on page body to prevent unnecessary re-renders
## Architecture
- `useResizablePanel` hook following the same pattern as
`useResizeTableHeader`
- `ResizablePanelEdge` - resize handle positioned at panel edge
- `ResizablePanelGap` - resize handle in the gap between panels
- `cssVariableEffect` - Recoil effect to sync CSS variables with state
## Refactoring
- Split `recoil-effects.ts` into separate files in `utils/recoil/` (one
export per file)
- Persist panel widths to localStorage via existing `localStorageEffect`
