Address Copilot review feedback on PR #46

- build.gradle.kts: use maxOf(flutter.minSdkVersion, 23) to preserve
  the floor required by oauth2_client/flutter_web_auth_2
- DEVELOPER.md: replace hardcoded /opt/homebrew paths with
  $(brew --prefix) for Intel Mac compatibility, use $HOME instead
  of /Users/$USER for --sdk_root
- README.md: label quick-start as macOS-specific, add cross-platform
  pointer to DEVELOPER.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

DEVELOPER.md

@@ -832,13 +832,13 @@ printf "\n24333f8a63b6825ea9c5514f83c2829b004d1fee" > ~/Library/Android/sdk/lice
 printf "\n84831b9409646a918e30573bab4c9c91346d8abd" > ~/Library/Android/sdk/licenses/android-sdk-preview-license
 
 # 3. Install platform tools and the SDK platform Flutter needs
-/opt/homebrew/share/android-commandlinetools/cmdline-tools/latest/bin/sdkmanager \
+"$(brew --prefix android-commandlinetools)/cmdline-tools/latest/bin/sdkmanager" \
-  --sdk_root=/Users/$USER/Library/Android/sdk \
+  --sdk_root="$HOME/Library/Android/sdk" \
   "platform-tools" "platforms;android-36" "build-tools;35.0.0"
 
 # 4. Copy cmdline-tools into the SDK root (Flutter expects them there)
 mkdir -p ~/Library/Android/sdk/cmdline-tools
-cp -R /opt/homebrew/share/android-commandlinetools/cmdline-tools/latest \
+cp -R "$(brew --prefix android-commandlinetools)/cmdline-tools/latest" \
   ~/Library/Android/sdk/cmdline-tools/latest
 
 # 5. Point Flutter at the SDK and accept licenses

README.md

@@ -90,7 +90,7 @@ A comprehensive Flutter app for mapping public surveillance infrastructure with
 - Code organization and contribution guidelines
 - Debugging tips and troubleshooting
 
-**Quick setup:**
+**Quick setup (macOS with Homebrew):**
 ```shell
 brew install --cask flutter        # Install Flutter SDK
 brew install cocoapods             # Required for iOS
@@ -99,6 +99,7 @@ flutter pub get                    # Install dependencies
 cp build_keys.conf.example build_keys.conf  # Add your OSM OAuth2 client IDs
 ./do_builds.sh                     # Build both platforms
 ```
+See [DEVELOPER.md](DEVELOPER.md) for cross-platform instructions and Android SDK setup.
 
 **Releases**: The app uses GitHub's release system for automated building and store uploads. Simply create a GitHub release and use the "pre-release" checkbox to control whether builds go to app stores - checked for beta releases, unchecked for production releases.
 

android/app/build.gradle.kts

@@ -39,7 +39,7 @@ android {
         // ────────────────────────────────────────────────────────────
         // oauth2_client 4.x & flutter_web_auth_2 5.x require minSdk 23
         // ────────────────────────────────────────────────────────────
-        minSdk = flutter.minSdkVersion
+        minSdk = maxOf(flutter.minSdkVersion, 23)
         targetSdk = 36
 
         // Flutter tool injects these during `flutter build`