Slack: Selecting a suggested correction does nothing and leaves the popup stuck

**Describe the bug**
In the Slack desktop app, Harper correctly highlights misspelled or grammatically incorrect words. However, selecting a suggested correction from the popup does not replace the word or close the popup.

The popup then remains stuck. The only workaround I have found is to toggle Harper off from the macOS menu bar and quit the app.

**To Reproduce**
Steps to reproduce the behavior:
1. Launch Harper and ensure it is enabled from the macOS menu bar.
2. Open the Slack desktop app.
3. Type a message containing a spelling or grammatical mistake.
4. Click the word highlighted by Harper.
5. Select one of the suggested corrections.Observe that the correction is not applied and the popup remains open.

**Expected behavior**
The selected suggestion should replace the highlighted word, and the suggestion popup should close.

**Platform**
Application: Slack desktop app for macOS v4.51.191
OS: macOS Tahoe 26.6.2
Harper version: 2.8.0
Accessibility permission: Enabled

**Additional context**
I installed Harper yesterday and granted the requested permissions. I do not have Grammarly or any other comparable writing assistance tool installed, so there should not be interference from another similar application.

Reproduce the issue in Slack desktop app for macOS v4.51.191 with Harper 2.8.0, following the listed steps and confirming Accessibility permission is enabled. Trace the suggestion-selection interaction from the Slack integration entry point; done means the selected correction replaces the word and the popup closes.

Written by the indexing model from the issue text.