refactor: Unify OSS update path through OSSUpdateStrategy

[JusterZhu]

Summary

GeneralUpdateBootstrap.LaunchAsync() bypasses the implemented OSSUpdateStrategy for the client-side OSS flow, calling LaunchOssAsync() directly. This creates two separate OSS code paths.

Current State

• LaunchAsync() switch case: AppType.OSS => await LaunchOssAsync()
• LaunchOssAsync() has its own version-check, download, and process-launch logic
• OSSUpdateStrategy is fully implemented with hooks, reporter, and download orchestrator support but only triggered via the IPC path (when GlobalConfigInfoOSS env variable is set)

Expected

1. LaunchAsync() for OSS should go through LaunchWithStrategy(new OSSUpdateStrategy()) just like Client and Upgrade
2. All OSS logic (version check, download, decompress, launch) lives in OSSUpdateStrategy
3. Delete LaunchOssAsync() from GeneralUpdateBootstrap
4. OSS path benefits from hooks, reporter, and download orchestrator like Client/Upgrade paths do

Benefits

• Single code path for OSS updates
• Consistent hooks + reporter invocation across all AppType values
• Less maintenance burden

Ref

Refactoring plan v2: Section 2.3 (Target Architecture), Sub Issue 3 (Bootstrap Unification)