Update site selection behavior after site deletion

[gcsecsey]

• Update site selection logic to preserve the currently selected site if it still exists after deletion.
• Add tests to verify that the first remaining site is selected when the currently selected site is deleted, and that selection remains unchanged when a different site is deleted.

Related issues

• Fixes STU-1241

Proposed Changes

• Updated onDeleteSite to check if the currently selected site still exists after deletion
• If the selected site still exists (user switched to another site), the selection is preserved
• If the selected site was deleted, it switches to the first remaining site
• Added unit tests to verify both scenarios

Testing Instructions

1. Start Studio with npm start
2. Create three sites (Site 1, Site 2, Site 3)
3. Delete Site 3
4. While the deletion is going on, quickly select Site 2
5. Check that Site 2 remains selected, and the selection doesn't change to Site 1

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

[wpmobilebot]

📊 Performance Test Results

Comparing 17075a3 vs trunk

site-editor

Metric	trunk	17075a3	Diff	Change
load	2883.00 ms	2876.00 ms	-7.00 ms	🟢 -0.2%

site-startup

Metric	trunk	17075a3	Diff	Change
siteCreation	7092.00 ms	7082.00 ms	-10.00 ms	🟢 -0.1%
siteStartup	3938.00 ms	3934.00 ms	-4.00 ms	🟢 -0.1%

---

Results are median values from multiple test runs.

Legend: 🟢 Improvement (faster) | 🔴 Regression (slower) | ⚪ No change

[ivan-ottinger]

Nice! Works well and the change looks good. Thank you for adding the test as well.

CleanShot.2026-01-22.at.15.38.30.mp4

[epeicher]

Thanks for fixing this @gcsecsey! I have tested it, and it works as advertised. I can see that the second site remains selected using this branch while it selects the first site in trunk. LGTM!

Trunk	This branch

[wojtekn]

It seems it still changes the tab to Overview for the selected site.

[gcsecsey]

It seems it still changes the tab to Overview for the selected site.

Good catch, I added a follow-up for this in #2468