content: create demo vault with splash art and feature showcase pages

8 files: index.md with wiki-links, features overview, navigation guide,
markdown showcase (all constructs), about page, changelog, and two
guides (sysop handbook, writing content) in a subdirectory. Includes
ANSI art splash.txt for the index page header.

vault/navigation-guide.md

@@ -0,0 +1,67 @@
+---
+description: How to navigate like a SysOp
+---
+
+# Navigation Guide
+
+Master the keyboard and browse your vault like a true SysOp.
+
+## Scrolling
+
+| Key          | Action              |
+|--------------|---------------------|
+| `j` / Down   | Scroll down one line |
+| `k` / Up     | Scroll up one line   |
+| `PgDn`       | Scroll down one page |
+| `PgUp`       | Scroll up one page   |
+
+## Link Navigation
+
+BBS-MD uses a **modal link navigation** system:
+
+1. Press **Tab** to enter link mode
+2. A highlight appears on the first link
+3. Use **Up/Down** arrows (or `j`/`k`) to cycle between links
+4. Press **Enter** to follow the selected link
+5. Press **Tab** or **Esc** to exit link mode
+
+> In link mode, the status bar updates to show link-specific hints. Watch the bottom of your screen for context.
+
+## Page Navigation
+
+| Key              | Action             |
+|------------------|---------------------|
+| Left / Backspace | Go back in history  |
+| Right            | Go forward in history |
+| Alt+Left         | Go back (always)    |
+| Alt+Right        | Go forward (always) |
+
+History works like a web browser. Following a new link from a mid-history position forks the history — forward entries are discarded.
+
+## Directory Page
+
+The [[Directory]] page behaves differently:
+
+- You're **always** in link mode on the directory page
+- Up/Down arrows cycle through document entries
+- Enter opens the selected document
+- **Esc** navigates back to the previous page
+- Tab has no effect (link mode can't be toggled off)
+
+## Quitting
+
+| Key            | Action                            |
+|----------------|-----------------------------------|
+| `q`            | Quit immediately (normal mode)    |
+| `Ctrl+C` x2   | Quit with confirmation (always)   |
+
+In **login shell mode**, `q` is disabled. You must use double `Ctrl+C` to disconnect.
+
+## Tips
+
+- The **breadcrumb** in the status bar shows your current location
+- **File metadata** (last modified date and size) appears on the right side of the status bar
+- Links that can't be resolved appear in ~~red strikethrough~~
+- The vault is **live** — edit a file externally and the page refreshes automatically
+
+Back to [[index|home]] or see [[Features]].