Updater often blocks on app exe still in use

### Short summary

_No response_

### Affected version or release

1.0.17 (last I updated from)

### Installation context

_No response_

### What happened?

Lately, whenever an update is downloaded and I restart the app to install it (by clicking on the Restart Now button in the in-app notification), the installer ends up blocking in the middle of the installation because the app exe is still running. I have to wait a non-insignificant amount of time (say, ~30s) before I can retry and continue the installation. This has started happening consistently in the past 10 days or so.

### Steps to reproduce

_No response_

### Expected behavior

I'd expect the installer to wait until the process is closed before starting the update installation.

### Additional context

_No response_

Start with the Restart Now button flow and the installer handoff, then reproduce an update from version 1.0.17 while checking when the app exe process exits. Done means the installer waits for the process to close and continues installation without requiring a manual retry.

索引モデルが issue の本文から書いたものです。