feat: wire extension points, remove dead code, fix bugs

Extension point wiring (7 wired):
- Strategy<T> → custom OS-level strategy via SetOsStrategy/ResolveOsStrategy
- SslPolicy<T> → VersionService.SetSslValidationPolicy()
- UpdateAuth<T> → VersionService.SetDefaultAuthProvider()
- DownloadOrchestrator<T> → replaces default batch download orchestrator
- DownloadPolicy<T> → custom retry policy (DefaultDownloadOrchestrator)
- DownloadExecutor<T> → custom file download executor
- DownloadPipeline<T> → per-asset pipeline factory with hash injection

Removed extension points (3):
- PipelineFactory<T> — no implementation, misleading name
- UpdateReporter<T> — redundant with Hooks<T>
- ConfigureBlackList — redundant with Configinfo fields
- CleanStrategy<T>/DirtyStrategy<T>/BinaryDiffer<T> — dead code

Dead code removed (13 files):
- ICleanStrategy/IDirtyStrategy + DefaultCleanStrategy/DefaultDirtyStrategy
- IStorageManager/DefaultStorageManager
- IUpdatePipelineFactory
- ObjectTranslator class
- ConfigurationMapper.CopyBaseFields()
- BlackListConfigBuilder
- DiffPipelineOptions.DeletePatchAfterApply
- PipelineContext unused "Name" key

Bug fixes:
- OssDownloadSource: missing HasMainUpdate/HasUpgradeUpdate flags
- OssDownloadSource: zip filename missing dot ("namezip" → "name.zip")

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: JusterZhu