T2: Eliminate GeneralClientBootstrap — merge into GeneralUpdateBootstrap with AppType

[JusterZhu]

Goal

Per the v2 refactoring plan, eliminate \GeneralClientBootstrap\ by merging all client-side functionality into \GeneralUpdateBootstrap. Use \AppType\ to dispatch between Client and Upgrade workflows.

Key Differences to Merge

GeneralClientBootstrap has these features not present in GeneralUpdateBootstrap:

1. Bowl process management — \CallSmallBowlHome()\ kills old Bowl processes
2. Custom options — \AddCustomOption()\ for pre-update custom operations
3. Richer skip callback — \AddListenerUpdatePrecheck()\ receives UpdateInfoEventArgs
4. Silent mode — delegates to SilentUpdateMode when enabled
5. Dual version validation — validates both client and upgrade versions
6. Failure check — \CheckFail()\ prevents re-updating to known-failed versions
7. ProcessInfo IPC creation — serializes update context for the upgrade process
8. StartApp — launches the main application after update

Tasks

1. Add client-side features to \GeneralUpdateBootstrap, gated by AppType=Client
2. Mark \GeneralClientBootstrap\ as [Obsolete]
3. Update any internal references
4. Verify full solution compiles

Part of GeneralUpdate v2 refactoring plan.