Initial implementation of slider

Single-file markdown slideshow for the terminal. Parses slides split by
`---`, renders each with glow, and navigates with n/p/q or arrow keys.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SPEC.md

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+# Terminal Slide Presentation Tool (slider)
+
+## 🎯 Purpose
+
+Create a standalone terminal-based slide presentation tool using `glow` as the markdown renderer. This tool will allow users to navigate slides via keyboard shortcuts (`n`, `p`, `q`)
+and showcase `glow`'s features like syntax highlighting, tables, and code blocks.
+
+## ✅ Features
+
+- Slide navigation (`n`, `p`, `q`)
+- Markdown rendering using `glow`
+- Support for `glow`-friendly features (code blocks, tables, syntax highlighting)
+- Modular structure for future expansion
+
+## 📁 Project Structure
+
+- `/SPEC.md`: Project specification and roadmap
+- `/examples/`: Test files showcasing `glow` features
+
+## 🚀 Next Steps
+
+1. Implement the navigation script
+2. Add support for slide timing or auto-advance
+3. Integrate with a markdown editor for live preview
+4. Add slide transitions or visual effects
+
+## 📌 Notes
+
+- This project is a lightweight tool for terminal use. For advanced features, consider using `reveal.js` or `remark` in a browser.