Address PR #274 feedback: improve JdkInstaller robustness

- Fix GetStringAsync to use GetAsync + ReadAsStringAsync for cancellation support
- Improve tar argument escaping using single quotes for paths with special chars
- Implement rollback logic: restore previous JDK if move fails
- Document .NET Standard 2.0 ZipFile cancellation limitation

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: rmarinho

src/Xamarin.Android.Tools.AndroidSdk/JdkInstaller.cs

@@ -219,7 +219,9 @@ public async Task InstallAsync (int majorVersion, string targetPath, IProgress<J
 
 			// Try to fetch checksum
 			try {
-				var checksumContent = await httpClient.GetStringAsync (versionInfo.ChecksumUrl).ConfigureAwait (false);
+				using var checksumResponse = await httpClient.GetAsync (versionInfo.ChecksumUrl, cancellationToken).ConfigureAwait (false);
+				checksumResponse.EnsureSuccessStatusCode ();
+				var checksumContent = await checksumResponse.Content.ReadAsStringAsync ().ConfigureAwait (false);
 				versionInfo.Checksum = ParseChecksumFile (checksumContent);
 				logger (TraceLevel.Verbose, $"Checksum for JDK {majorVersion}: {versionInfo.Checksum}");
 			}
@@ -465,6 +467,10 @@ async Task ExtractArchiveAsync (string archivePath, string targetPath, Cancellat
 				Directory.CreateDirectory (tempExtractPath);
 
 				if (OS.IsWindows) {
+					// Note: ZipFile.ExtractToDirectory in .NET Standard 2.0 does not support cancellation tokens.
+					// This is a .NET API limitation. The tar extraction on Unix/macOS does support cancellation.
+					// For very large archives, consider implementing entry-by-entry extraction if cancellation
+					// responsiveness on Windows becomes critical.
 					ZipFile.ExtractToDirectory (archivePath, tempExtractPath);
 				}
 				else {
@@ -483,23 +489,46 @@ async Task ExtractArchiveAsync (string archivePath, string targetPath, Cancellat
 						jdkRoot = contentsHome;
 				}
 
-				// Move to final destination (atomic swap to avoid Windows race condition)
+				// Move to final destination with rollback on failure
+				string? backupPath = null;
 				if (Directory.Exists (targetPath)) {
-					var backupPath = targetPath + $".old-{Guid.NewGuid ():N}";
+					backupPath = targetPath + $".old-{Guid.NewGuid ():N}";
 					Directory.Move (targetPath, backupPath);
-					try {
-						Directory.Delete (backupPath, recursive: true);
-					}
-					catch (Exception ex) {
-						logger (TraceLevel.Warning, $"Could not clean up old JDK at '{backupPath}': {ex.Message}");
-					}
 				}
 
 				var parentDir = Path.GetDirectoryName (targetPath);
 				if (!string.IsNullOrEmpty (parentDir))
 					Directory.CreateDirectory (parentDir);
 
-				Directory.Move (jdkRoot, targetPath);
+				try {
+					Directory.Move (jdkRoot, targetPath);
+
+					// Only delete backup after successful move
+					if (backupPath != null && Directory.Exists (backupPath)) {
+						try {
+							Directory.Delete (backupPath, recursive: true);
+						}
+						catch (Exception ex) {
+							logger (TraceLevel.Warning, $"Could not clean up old JDK at '{backupPath}': {ex.Message}");
+						}
+					}
+				}
+				catch (Exception ex) {
+					// Rollback: restore the original JDK from backup
+					logger (TraceLevel.Error, $"Failed to move JDK to '{targetPath}': {ex.Message}");
+					if (backupPath != null && Directory.Exists (backupPath)) {
+						try {
+							if (Directory.Exists (targetPath))
+								Directory.Delete (targetPath, recursive: true);
+							Directory.Move (backupPath, targetPath);
+							logger (TraceLevel.Warning, $"Restored previous JDK from backup '{backupPath}'.");
+						}
+						catch (Exception restoreEx) {
+							logger (TraceLevel.Error, $"Failed to restore previous JDK from backup '{backupPath}': {restoreEx.Message}");
+						}
+					}
+					throw;
+				}
 			}
 			finally {
 				if (Directory.Exists (tempExtractPath))
@@ -511,9 +540,13 @@ async Task ExtractArchiveAsync (string archivePath, string targetPath, Cancellat
 
 		async Task ExtractTarGzAsync (string archivePath, string destinationPath, CancellationToken cancellationToken)
 		{
+			// Use single quotes to properly handle paths with special characters on Unix shells
+			var escapedArchivePath = archivePath.Replace ("'", "'\\''");
+			var escapedDestinationPath = destinationPath.Replace ("'", "'\\''");
+
 			var psi = new ProcessStartInfo {
 				FileName = "tar",
-				Arguments = $"-xzf \"{archivePath}\" -C \"{destinationPath}\"",
+				Arguments = $"-xzf '{escapedArchivePath}' -C '{escapedDestinationPath}'",
 				UseShellExecute = false,
 				CreateNoWindow = true,
 			};