Fix blank Applications icon in DMG installer

Switch from npm create-dmg (sindresorhus) to brew create-dmg
(create-dmg/create-dmg) which properly renders the Applications
folder symlink icon with explicit layout control.

.github/workflows/release.yml

@@ -44,7 +44,7 @@ jobs:
         run: |
           brew update
           brew install zig
-          npm install --global create-dmg
+          brew install create-dmg
 
       - name: Build GhosttyKit.xcframework
         run: |
@@ -160,12 +160,23 @@ jobs:
           xcrun stapler validate "$APP_PATH"
           spctl -a -vv --type execute "$APP_PATH"
           rm -f "$ZIP_SUBMIT"
-          # create-dmg generates a styled drag-to-install DMG (matches Ghostty's approach)
+          # create-dmg (brew) generates a styled drag-to-install DMG
+          # It expects: create-dmg [options] <output.dmg> <source_folder>
+          # --no-internet-enable avoids deprecated flag warning
+          DMG_SOURCE="$(mktemp -d)"
+          cp -R "$APP_PATH" "$DMG_SOURCE/"
           create-dmg \
-            --identity="$APPLE_SIGNING_IDENTITY" \
-            "$APP_PATH" \
-            ./
-          mv ./cmuxterm*.dmg "$DMG_RELEASE"
+            --volname "cmuxterm" \
+            --window-pos 200 120 \
+            --window-size 660 400 \
+            --icon-size 160 \
+            --icon "cmuxterm.app" 180 170 \
+            --app-drop-link 480 170 \
+            --no-internet-enable \
+            --codesign "$APPLE_SIGNING_IDENTITY" \
+            "$DMG_RELEASE" \
+            "$DMG_SOURCE"
+          rm -rf "$DMG_SOURCE"
           DMG_SUBMIT_JSON="$(xcrun notarytool submit "$DMG_RELEASE" --apple-id "$APPLE_ID" --team-id "$APPLE_TEAM_ID" --password "$APPLE_APP_SPECIFIC_PASSWORD" --wait --output-format json)"
           DMG_SUBMIT_ID="$(python3 -c 'import json,sys; print(json.load(sys.stdin)["id"])' <<<"$DMG_SUBMIT_JSON")"
           DMG_STATUS="$(python3 -c 'import json,sys; print(json.load(sys.stdin)["status"])' <<<"$DMG_SUBMIT_JSON")"