Document macOS quarantine workaround in README

macOS Gatekeeper blocks unsigned apps with "damaged" error.
Added xattr -cr command to Troubleshooting section.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -267,6 +267,15 @@ Both workflows require a `BUILD_TOKEN` secret in the repo settings (Gitea API to
 
 ## Troubleshooting
 
+### macOS: "App is damaged and can't be opened"
+macOS Gatekeeper blocks unsigned applications. Since the app is not yet signed with an Apple Developer certificate, you need to remove the quarantine flag before opening:
+
+```bash
+xattr -cr "/Applications/Local Transcription.app"
+```
+
+Then open the app normally. You only need to do this once after downloading.
+
 ### Model Loading Issues
 - Models download automatically on first use to `~/.cache/huggingface/`
 - First run requires internet connection