Fail InstallAndroidDependencies cleanly when ResolveAndroidTooling has no resolved SDK

[Copilot]

InstallAndroidDependencies could exit successfully even when a required platform package was still missing. On a fresh SDK/JDK path, ResolveAndroidTooling could dereference an unresolved SDK state, emit XARAT7001, and leave dependency installation to continue as warnings instead of producing a hard failure.

• What changed

  • ResolveAndroidTooling now checks that SDK resolution actually produced a usable MonoAndroidHelper.AndroidSdk and AndroidSdkPath before probing build-tools / cmdline-tools paths.
  • When that state is missing, the task logs the normal XA5300 Android SDK error and returns false instead of throwing XARAT7001 from a NullReferenceException.

• Why this matters

  • InstallAndroidDependencies now gets a real task failure signal when SDK tooling resolution has not succeeded.
  • This prevents the previous "warning chain + exit 0" behavior that allowed missing required packages such as platforms;android-37.0 to surface only later as XA5207.

• Focused coverage

  • Added a task-level regression test for the missing-resolved-SDK state.
  • The test asserts that ResolveAndroidTooling:
    • fails deterministically,
    • still computes AndroidApiLevel for dependency resolution,
    • reports XA5300,
    • does not report XARAT7001.

var androidSdk = MonoAndroidHelper.AndroidSdk;
if (androidSdk == null || AndroidSdkPath.IsNullOrEmpty ()) {
	Log.LogCodedError ("XA5300", Properties.Resources.XA5300_Android_SDK);
	return false;
}