docs: rewrite README with full project documentation

Co-authored-by: Cursor <cursoragent@cursor.com>

README.md

@@ -1,7 +1,69 @@
-# Tauri + SvelteKit + TypeScript
+# GUI Video Clipper
 
-This template should help get you started developing with Tauri, SvelteKit and TypeScript in Vite.
+A macOS desktop app for clipping segments from online videos. Paste a URL, scrub the timeline, mark your clips, and export — without manually downloading the video first.
 
-## Recommended IDE Setup
+## Features
 
-[VS Code](https://code.visualstudio.com/) + [Svelte](https://marketplace.visualstudio.com/items?itemName=svelte.svelte-vscode) + [Tauri](https://marketplace.visualstudio.com/items?itemName=tauri-apps.tauri-vscode) + [rust-analyzer](https://marketplace.visualstudio.com/items?itemName=rust-lang.rust-analyzer).
+- **URL Input** — Paste a YouTube (or other supported) URL and start working immediately
+- **Video Preview** — Scrub, seek, and frame-step through the video with full transport controls
+- **Mark In/Out** — Set clip boundaries with keyboard shortcuts (I/O) or transport buttons
+- **Timeline** — Visual timeline with waveform display and thumbnail strip
+- **Clip Export** — Export clips in lossless (stream copy) or precise (re-encode) modes
+- **Captions** — Download subtitles, preview with karaoke-style highlighting, burn into exports
+- **Setup Wizard** — Automatically detects and installs required dependencies (ffmpeg, yt-dlp)
+
+## Prerequisites
+
+- **macOS** (primary target platform)
+- **Node.js** (v18+)
+- **Rust** toolchain ([rustup.rs](https://rustup.rs))
+
+ffmpeg and yt-dlp are detected (and can be installed) automatically by the built-in setup wizard on first launch.
+
+## Build & Run
+
+```bash
+# Install frontend dependencies
+npm install
+
+# Development (hot-reload)
+npm run tauri dev
+
+# Production build
+npm run tauri build
+```
+
+## Architecture
+
+GUI Video Clipper is built with [Tauri v2](https://v2.tauri.app/) (Rust backend) and [Svelte 5](https://svelte.dev/) (TypeScript frontend).
+
+### Backend (Rust)
+
+- **Video Resolver** — Resolves URLs via yt-dlp, extracts metadata and stream URLs
+- **Download Manager** — Manages preview and high-quality downloads with progress tracking
+- **Media Server** — Local HTTP server for streaming video to the frontend player
+- **Waveform Generator** — Extracts audio waveform data at multiple zoom tiers via ffmpeg
+- **Thumbnail Extractor** — Generates timeline thumbnail strips from keyframes
+- **Export Pipeline** — Handles clip extraction with ffmpeg (lossless and precise modes)
+- **Subtitle Downloader** — Fetches and converts subtitles for preview and burn-in
+
+### Frontend (Svelte 5 + TypeScript)
+
+- **Timeline** — Canvas-based timeline with waveform, thumbnails, and clip region rendering
+- **Transport Controls** — Play/pause, seek, frame-step, shuttle (J/K/L), keyboard shortcuts
+- **Video Player** — HTML5 video element connected to the local media server
+- **Export Dialog** — Configure and execute clip exports with progress tracking
+- **Caption Settings** — Font, color, shadow, and positioning controls for subtitle burn-in
+
+## Contributing
+
+1. Fork the repository
+2. Create a feature branch (`git checkout -b feat/my-feature`)
+3. Make your changes
+4. Run checks: `npm run check`
+5. Commit with a descriptive message
+6. Open a pull request
+
+## License
+
+[MIT](LICENSE)