docs: document navigation, TOC, and template context

Add comprehensive documentation for recently implemented features:
- [nav] config section (nested, toc toggles)
- Complete frontmatter fields reference (10 fields)
- Hierarchical navigation behavior with ASCII diagram
- Template context: nested_nav, anchors array, page.toc
- Nav item structure including children for nested menus

docs/content/configuration.md

@@ -40,6 +40,25 @@ sukr -c sites/blog/site.toml
 # Paths resolve relative to sites/blog/
 ```
 
+## Navigation Configuration
+
+Control how navigation menus are generated:
+
+```toml
+[nav]
+nested = false  # Show child pages under sections
+toc    = false  # Enable table of contents globally
+```
+
+| Field    | Default | Description                                         |
+| -------- | ------- | --------------------------------------------------- |
+| `nested` | `false` | Display section children as nested sub-menus        |
+| `toc`    | `false` | Show heading anchors in sidebar (table of contents) |
+
+When `nested = true`, section pages appear as indented sub-items under their parent section. When `toc = true`, h2-h6 headings are extracted and displayed as anchor links in the sidebar.
+
+Both settings can be overridden per-page via frontmatter.
+
 ## CLI Options
 
 ```bash
@@ -62,9 +81,26 @@ weight: 10 # Sort order (lower = first)
 nav_label: Short Name # Override nav display
 section_type: blog # Override section template
 template: custom # Override page template
+toc: true # Override global TOC setting
+link_to: https://... # External link (for project cards)
 ---
 ```
 
+### Frontmatter Fields
+
+| Field          | Type    | Description                                    |
+| -------------- | ------- | ---------------------------------------------- |
+| `title`        | string  | Page title (required)                          |
+| `description`  | string  | Meta description                               |
+| `date`         | string  | Publication date (YYYY-MM-DD)                  |
+| `weight`       | integer | Sort order (lower = first, default 50)         |
+| `nav_label`    | string  | Override navigation label (defaults to title)  |
+| `section_type` | string  | Template dispatch (e.g., "blog", "projects")   |
+| `template`     | string  | Custom template path                           |
+| `toc`          | boolean | Enable/disable table of contents for this page |
+| `link_to`      | string  | External URL (renders as link instead of page) |
+| `tags`         | list    | Tags for categorization                        |
+
 ### Section Types
 
 The `section_type` field determines which template is used for section indexes: