Localization: "Add Locale" does not refresh its already-in-project state, so a locale added elsewhere while the window is open can be added a second time

Steps to reproduce:

1. Create a new project
2. Install the Localization package (com.unity.localization)
3. Open Edit > Project Settings > Localization and click "Create" to make the settings asset
4. Click "Add Locale", add English, and save it into a project folder
5. Click "Add Locale" again and leave the window open. Note that English is greyed out and Japanese is selectable
6. Without closing that window, add Japanese to the project by another route — click "Add Custom Locale" in Project Settings > Localization and create a locale with the identifier ja
7. Return to the still-open "Add Locale" window. The Japanese row is still shown as selectable
8. Tick Japanese, click "Add Locales", choose a folder, and inspect the Project window and "Available Locales"

Actual results: The window keeps the state each row had when it was opened and never refreshes it. Japanese still reads as selectable although it is now in the project, and adding it creates a second Locale asset for a culture that already exists. The same staleness applies in the other direction: if a Locale asset is deleted in the Project window while "Add Locale" is open, its row stays greyed out and cannot be re-added until the window is reopened

Expected results: The list refreshes when the window regains focus or when the project's Locale assets change, so already-added locales are greyed out and removed ones become selectable again

Reproducible with versions: 1.5.12 (6000.5.7f1, 6000.6.0f1, 6000.7.0a6)

Tested on (OS): MacBook Pro - Tahoe 26.6.2

Notes:

• Two directions, different impact. The deleted-asset case is an inconvenience - reopening the window clears it. The added-elsewhere case creates duplicate data