add release script to dmg

README.md

@@ -63,6 +63,7 @@ Click the preview above to watch the demo recording.
 - macOS 14 or later
 - Xcode 16 or later
 - Homebrew `xcodegen`
+- Homebrew `create-dmg` for release `.dmg` packaging
 
 ### Build
 
@@ -81,6 +82,33 @@ DEVELOPER_DIR=/Applications/Xcode.app/Contents/Developer \
   xcodebuild build -project CommandNotch.xcodeproj -scheme CommandNotch -destination 'platform=macOS'
 ```
 
+### Build a release `.dmg`
+
+Use `create-dmg` to build the styled Finder installer window with the usual drag-to-`Applications` layout.
+
+Install the packaging dependency once:
+
+```bash
+brew install create-dmg
+```
+
+Then build from the `app/` directory:
+
+```bash
+./scripts/build-release-dmg.sh
+```
+
+That produces:
+
+- `releases/CommandNotch YYYY-MM-DD HH-MM-SS/CommandNotch.app`
+- `releases/CommandNotch YYYY-MM-DD HH-MM-SS/CommandNotch.dmg`
+
+Notes:
+
+- The script regenerates the Xcode project, archives the Release build, then packages the archived app into a styled `.dmg`.
+- The archive is written to `/tmp` and is only used as the source for the exported `.app`.
+- If you want a distributable build signed with a specific identity, make sure your Xcode signing settings are configured before running the archive step.
+
 ## Project Layout
 
 ```text