Setup dev env: Android CLI tools docs and Valdi CLI improvements

[busybox11]

Since devs will need to setup some parts of the Android SDK themselves beforehand, as instructed in the MacOS and Linux setup guide, this PR adds a notice to install the latest Android SDK CLI Tools from the SDK Manager as well.

This PR also removes the manual download, unzip, copy and handling of the sdkmanager, but rather assumes the user has followed the setup guide and installed the tools from SDK Manager.

Fixes #1

[busybox11]

This assumes manual Android Studio setup is required.

In theory only the sdkmanager would be required to complete the installation, and manual selection of specific NDKs and tool versions is already handled by DevSetupHelper::setupAndroidSDK().

Those could be removed from the guide, lmk if I should add this as well - or if the manual Android Studio part should be removed instead, which could be a little more flaky. Went for the simplest option for now.

[kyle-ssg]

Beat me to it!

[ecoreng]

👍🏼

[sushilvisual]

Thanks for this cleanup — it’s a useful simplification and I appreciate moving away from brittle downloads. Before we can approve, please address the following changes:

1. Windows support: add a Windows-aware check/fallback for the Android SDK command-line tools. For example, verify sdkmanager.bat in %ANDROID_HOME%\\cmdline-tools\\latest\\bin or fall back to searching PATH for sdkmanager(.bat) so Windows developers aren’t blocked.

2. Improve the missing sdkmanager error message: make it actionable. Include a short install instruction and a link, for example:

   • "Open Android Studio → More Actions → SDK Manager → SDK Tools → Install ‘Android SDK Command-line Tools’."
   • For headless/container environments, link to the official docs: https://developer.android.com/studio/command-line/sdkmanager

3. (Optional but recommended) Add a small CI check or unit test (if possible) to catch regressions related to removed constants and the setupAndroidSDK path.

After these are addressed I’ll re-review. Thanks for the contribution — nice work so far.