# Spec: Navigation (Layer 06)

File: `src/layers/06-navigation.css`

## Purpose

Navigation patterns that go beyond the basic `nav` landmark. Sidebar navigation, table of contents, dropdown menus, navigation state management.

## Scope

### In scope
- `nav[data-nav="sidebar"]` — sidebar navigation tree
- `aside[data-toc]` — in-page table of contents
- Dropdown menus within navigation
- Active/current page indicators (`aria-current`)
- Mobile navigation patterns
- Navigation collapse/expand behavior

### Out of scope
- The `body > nav` landmark itself (→ landmarks layer)
- Breadcrumbs (→ components layer)

## Constraints

- References only semantic aliases from `01-tokens.css`
- Navigation must be keyboard-accessible
- Active states use `aria-current`, not classes