Round 2: Unit tests for Compress, HashAlgorithms, Download Executors, Network, Silent, and Strategy modules

[JusterZhu]

Overview

Follow-up to #423/#424. This issue tracks adding comprehensive AAA pattern unit tests for the remaining GeneralUpdate.Core modules.

Modules to cover

Module	Classes	Priority
Compress	CompressProvider, ZipCompressionStrategy	High
HashAlgorithms	HashAlgorithmBase, Sha256HashAlgorithm	High
Download	HttpDownloadExecutor, DefaultDownloadOrchestrator, DefaultDownloadPipeline, HttpDownloadSource, HubDownloadSource	High
Network	VersionService (retry/auth/SSL)	High
Silent	SilentPollOrchestrator	Medium
Strategy	AbstractStrategy, OS-level strategies	Medium
Pipeline	PatchMiddleware	Low

Test Pattern

• AAA (Arrange-Act-Assert)
• xUnit + Moq
• All tests passing on net10.0