Initial commit: Production-ready KoalaSync Monorepo with Manifest V3, Socket.IO Relay, and Two-Phase Sync

extension/README.md

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+# KoalaSync Chrome Extension
+
+A Manifest V3 Chrome Extension for synchronized video playback.
+
+## Key Features
+- **Manifest V3**: Using a modern Service Worker architecture.
+- **Native WebSockets**: No heavy libraries, uses the browser's native API.
+
+## Privacy & Permissions
+KoalaSync requires `<all_urls>` permission to detect and interact with video elements (`<video>`) on any website. 
+- **No Browsing History**: We do not track which sites you visit.
+- **No Telemetry**: There are no analytics or tracking scripts included.
+- **Local State**: Settings (Server URL, Room ID, Password) are stored only locally in your browser using `chrome.storage`.
+
+## Installation
+1. Go to `chrome://extensions/`.
+2. Enable **Developer mode**.
+3. Click **Load unpacked** and select this folder.
+
+## Development
+If you change `shared/constants.js`, remember to run the synchronization script:
+- Windows: `..\scripts\sync-constants.bat`
+- Linux/macOS: `../scripts/sync-constants.sh`