feat: scaffold howtos project

Collection of usage guides and cheatsheets. Includes project docs,
topic template, and directory structure.

docs/USAGE.md

@@ -0,0 +1,29 @@
+# Usage
+
+## Browsing Topics
+
+Each topic is a standalone Markdown file in `topics/`:
+
+```bash
+# List available topics
+ls topics/
+
+# Read a topic in terminal
+cat topics/git.md        # plain
+bat topics/git.md        # syntax highlighted
+glow topics/git.md       # rendered markdown
+```
+
+## Adding a New Topic
+
+```bash
+cp docs/TEMPLATE.md topics/<name>.md
+```
+
+Edit the file following the template structure. Keep it under 200 lines.
+
+## Naming Conventions
+
+- Lowercase, hyphenated: `docker-compose.md`, `git-rebase.md`
+- One topic per file
+- Use the tool/subject name as the filename