Add SDK bootstrap and sdkmanager wrapper

[rmarinho]

Summary

Adds SDK bootstrap and sdkmanager wrapper to Xamarin.Android.Tools.AndroidSdk, enabling programmatic Android SDK setup from scratch.

Closes #271

Architecture

Two-phase approach:

1. Bootstrap: Download command-line tools from manifest feed, SHA-1 verify, extract to cmdline-tools/<version>/
2. Manage: Use extracted sdkmanager CLI for all package operations

File Structure

SdkManager is split into focused partial classes for maintainability:

• SdkManager.cs - Core class, properties, constructor, dispose (~84 lines)
• SdkManager.Manifest.cs - Manifest download and XML parsing (~141 lines)
• SdkManager.Bootstrap.cs - SDK bootstrap/download/extract flow (~175 lines)
• SdkManager.Packages.cs - Package list/install/uninstall/update + output parsing (~228 lines)
• SdkManager.Licenses.cs - License accept/parse/check operations (~246 lines)
• SdkManager.Process.cs - Process execution, elevation, download, checksum, env config (~307 lines)

Supporting files:

• EnvironmentVariableNames.cs - Centralized constants for ANDROID_HOME, JAVA_HOME, etc.
• FileUtil.cs - Extended with chmod, recursive copy, executable permissions, elevation check
• Models/Sdk/*.cs - Data models: SdkPackage, SdkLicense, SdkManifestComponent, SdkBootstrapProgress
• .github/copilot-instructions.md - Updated coding conventions
• SdkManagerTests.cs - 534 lines of tests

Key Features

• Manifest-driven bootstrap: XmlReader-based parsing with platform/arch filtering
• ANDROID_USER_HOME: Sets ~/.android so sdkmanager writes install properties in user-writable location
• Elevated execution (Windows): Detects admin-protected paths, re-launches via UAC. Read-only ops skip elevation.
• Zip Slip protection: Entry-by-entry extraction with path traversal validation
• Rollback on failure: Backup existing installation, restore on extract/move failure
• Cross-device fallback: Directory.Move falls back to recursive copy
• SHA-1 checksum verification of downloaded archives
• p/invoke chmod with process fallback for Unix executable permissions
• ArrayPool buffers (net5.0+) for download operations
• netstandard2.0 + net10.0 compatible, full CancellationToken support
• ANDROID_SDK_ROOT deprecated per Android docs - only ANDROID_HOME is set
• File utilities consolidated in FileUtil.cs - no duplication across domain classes

Tests

89 tests pass (4 skipped). Covers manifest parsing, list output parsing, license parsing, error cases.

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

[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 9 comments.

[Copilot]

@rmarinho I've opened a new pull request, #288, to work on those changes. Once the pull request is ready, I'll request review from you.

[Copilot]

Pull request overview

Copilot reviewed 19 out of 19 changed files in this pull request and generated 7 comments.

[Copilot]

In the generated elevated .cmd script, "{sdkManagerPath}" {escapedArgs} will typically point to sdkmanager.bat. Calling a .bat from within another .cmd file without call terminates the wrapper script early, so the echo %ERRORLEVEL% > "{exitCodeFile}" line never runs and failures can be reported as success. Prefix the sdkmanager invocation with call (or invoke it via cmd /c) so the wrapper continues and captures the real exit code.

Suggested change

	{licenseInput}"{sdkManagerPath}" {escapedArgs} > "{stdoutFile}" 2> "{stderrFile}"
	{licenseInput}call "{sdkManagerPath}" {escapedArgs} > "{stdoutFile}" 2> "{stderrFile}"

[Copilot]

StartShellExecuteProcessAsync() passes the CancellationToken to Task.Run, but if cancellation occurs while waiting, the task can be canceled without killing the spawned process. This can leave an elevated cmd.exe (and child sdkmanager) running after the caller cancels. Consider registering the token to KillProcess(process) (similar to StartProcess) and ensure cancellation triggers process termination before returning/throwing.

Suggested change

	await Task.Run (() => {
	if (!process.WaitForExit ((int) timeout.TotalMilliseconds)) {
	KillProcess (process);
	throw new TimeoutException ($"Process timed out after {timeout.TotalMinutes} minutes.");
	}
	}, cancellationToken).ConfigureAwait (false);
	using (cancellationToken.Register (() => KillProcess (process))) {
	await Task.Run (() => {
	if (!process.WaitForExit ((int) timeout.TotalMilliseconds)) {
	KillProcess (process);
	throw new TimeoutException ($"Process timed out after {timeout.TotalMinutes} minutes.");
	}
	}).ConfigureAwait (false);
	}