**NavItem / NavSection** — building blocks of the left sidebar. Active item gets an accent rail, tint, and accent icon. `NavSection` is the uppercase group eyebrow. Count badges surface playout warnings / health errors.

```jsx
<NavSection>Scheduling</NavSection>
<NavItem icon={<Ico n="Tv"/>} label="Channels" active />
<NavItem icon={<Ico n="CalendarClock"/>} label="Playouts" badge={3} badgeTone="warn" />
```

Props (NavItem): `icon`, `label`, `active`, `badge`, `badgeTone` (warn·error·accent), `href`/`onClick`.
