Prevent crashes from partial in-place updates

[Gabriel Dufresne (GabrielDuf)]

This pull request introduces a mechanism to prevent application launches during in-progress updates, ensuring that UniGetUI does not start while its binaries are being replaced. It adds a file-based update-in-progress marker, logic to create and remove the marker during installation, and guards in both the Avalonia and classic entry points to abort startup if an update is detected. The update detection logic is fully tested, and installer process handling is improved to reliably terminate running instances and avoid file lock issues.

Update-in-progress detection and prevention:

• Added UpdateInProgressGuard class to UniGetUI.Core.Data that detects the presence of an update-in-progress marker file and blocks UI startup if an update is underway. The guard checks both the current and parent directories, ignores stale markers, and is used by both the Avalonia and classic entry points (UpdateInProgressGuard.cs, EntryPoint.cs, Program.cs).
• Added comprehensive tests for UpdateInProgressGuard to ensure correct detection logic, marker cleanup, and contract with the installer (UpdateInProgressGuardTests.cs).
• Exposed internals of UniGetUI.Core.Data to the test assembly via InternalsVisibleTo (InternalsVisibleTo.cs).

Installer improvements and integration:

• Modified the installer script (UniGetUI.iss) to write the update-in-progress marker before copying files and remove it after installation, ensuring that any instance launched mid-update will abort. The marker file name is kept in sync with the guard logic.
• Improved process handling in the installer: replaced the old TaskKill with a new TaskKillWait that reliably kills all relevant processes (including helpers), and set CloseApplications=force to forcibly close any processes holding files to be overwritten.

Installer deployment changes:

• Updated the installer to avoid redundant calls to kill running apps, since this is now handled in PrepareToInstall.

These changes collectively make UniGetUI more robust during updates, preventing accidental launches into a partially updated state and improving reliability.

[Copilot]

Pull request overview

Introduces an “update-in-progress” marker mechanism so UniGetUI won’t start while an in-place installer update is actively swapping binaries, reducing the risk of launching into a partially updated state.

Changes:

• Adds an UpdateInProgressGuard in UniGetUI.Core.Data and integrates it into both WinUI and Avalonia entry points to abort UI startup during updates.
• Updates the Inno Setup installer to create/remove an update marker around the file copy window and improves process termination prior to install.
• Adds unit tests for the guard and exposes internals to the test assembly.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
UniGetUI.iss	Adds update marker lifecycle in installer + improved process-kill behavior and close-apps configuration.
src/UniGetUI/EntryPoint.cs	Blocks WinUI startup when an update marker is detected.
src/UniGetUI.Core.Data/UpdateInProgressGuard.cs	New guard that detects (and optionally cleans) the update marker in base/parent directories.
src/UniGetUI.Core.Data/InternalsVisibleTo.cs	Allows the test project to call internal guard overloads.
src/UniGetUI.Core.Data.Tests/UpdateInProgressGuardTests.cs	Adds tests validating marker detection/cleanup and the installer contract.
src/UniGetUI.Avalonia/Program.cs	Blocks Avalonia startup when an update marker is detected.

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