Development environment setup (#165)

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## Description

Updated `AGENTS.md` to document the Flutter SDK installation path and
add comprehensive instructions for real-device testing using
BrowserStack. This ensures future agents and developers can easily set
up the environment and verify the application.

## Related Issue(s)

N/A

## Type of Change

- [ ] 🛠️ Bug fix (non-breaking change which fixes an issue)
- [ ] 🚀 New feature (non-breaking change which adds functionality)
- [ ] 💥 Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [x] 📝 Documentation
- [ ] 📈 Performance improvement
- [ ] 🏗️ Code refactoring
- [x] 🧹 Chore / Housekeeping

## Checklist

- [x] I have made corresponding changes to the documentation
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have updated the CHANGELOG.md under the "Unreleased" section

## Screenshots (if applicable)

<video src="/opt/cursor/artifacts/browserstack_real_device_demo.mp4"
controls></video>
Faro Flutter example app running on a real Google Pixel 8 (Android 14)
via BrowserStack -- navigating through home, features, and tracing
pages.

<img src="/opt/cursor/artifacts/01_home_screen.png" alt="Home screen
showing Faro Test App title and Change Route button" />
<img src="/opt/cursor/artifacts/02_features_page.png" alt="Features page
with User Settings, Sampling Settings, Tracing, User Actions cards" />
<img src="/opt/cursor/artifacts/03_features_scrolled.png" alt="Features
page scrolled showing all SDK feature buttons" />
<img src="/opt/cursor/artifacts/05_tracing_with_spans.png" alt="Tracing
page with Simple Span and Nested Spans log output" />

## Additional Notes

This update includes the Flutter SDK installation path and a detailed
guide on using BrowserStack for real-device verification, which was
performed to confirm the example app's functionality.

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<p><a
href="https://cursor.com/agents/bc-ffe49da4-03da-48dc-a4f0-38e9b182e34e"><picture><source
media="(prefers-color-scheme: dark)"
srcset="https://cursor.com/assets/images/open-in-web-dark.png"><source
media="(prefers-color-scheme: light)"
srcset="https://cursor.com/assets/images/open-in-web-light.png"><img
alt="Open in Web" width="114" height="28"
src="https://cursor.com/assets/images/open-in-web-dark.png"></picture></a>&nbsp;<a
href="https://cursor.com/background-agent?bcId=bc-ffe49da4-03da-48dc-a4f0-38e9b182e34e"><picture><source
media="(prefers-color-scheme: dark)"
srcset="https://cursor.com/assets/images/open-in-cursor-dark.png"><source
media="(prefers-color-scheme: light)"
srcset="https://cursor.com/assets/images/open-in-cursor-light.png"><img
alt="Open in Cursor" width="131" height="28"
src="https://cursor.com/assets/images/open-in-cursor-dark.png"></picture></a>&nbsp;</p>


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Author: robert-northmind

AGENTS.md

@@ -235,6 +235,10 @@ This is a client-side Flutter SDK with no server component. All unit tests run w
 
 Standard build/test commands are documented in the **Build/Test Commands** section above. Running `flutter pub get` at the workspace root also resolves `example/` dependencies (they share a workspace).
 
+### Flutter SDK
+
+Flutter is installed at `/opt/flutter`. The `PATH` is set in `~/.bashrc` to include `/opt/flutter/bin` and the bundled Dart SDK.
+
 ### Android SDK
 
 The Android SDK is installed at `/opt/android-sdk`. The `ANDROID_HOME` env var and PATH additions are set in `~/.bashrc`. Flutter is already configured to use this SDK via `flutter config --android-sdk`.
@@ -267,6 +271,10 @@ dart tool/pre_release_check.dart
 
 See `CONTRIBUTING.md` for the full contributor workflow.
 
+### Real-device testing via BrowserStack
+
+If `BROWSERSTACK_USERNAME` and `BROWSERSTACK_ACCESS_KEY` are set, the example APK can be tested on a real Android device using BrowserStack App Automate. Upload via the BrowserStack REST API with `custom_id=faro-flutter-example`, then use Appium REST calls to interact with the app. Flutter exposes UI elements through the Accessibility Bridge, so `accessibility id` element lookups work for buttons with text labels (e.g., `"Change Route"`, `"Simple Span"`). For card-style `ListTile` widgets, the accessibility label is the concatenated title and subtitle separated by `\n`.
+
 ### Gotchas
 
 - `flutter pub get` in the root resolves both SDK and `example/` dependencies due to workspace configuration — no need to run it separately in `example/`.