Renaming a non‑empty folder leaves empty ghost of old name in QGIS plugin tree (plugin 2025.4.0; web correct)

Description
Renaming a non‑empty project folder in a Mergin Maps–managed QGIS project causes the new folder name to appear, but an empty “ghost” of the old folder remains visible only in the Mergin Maps plugin project tree. The web dashboard correctly shows only the new folder name.

Scope:

• Affects non‑empty folders (contain files/subfolders before rename).
• Ghost folder appears only in the plugin tree, not on web.

Environment
Staging/PROD

Application (+ app version, build, operating system)
QGIS versions:

• QGIS version: 3.40.5-Bratislava

Mergin Maps plugin:

• Plugin version: 2025.4.0 (PROD)

My operating system:

• macOS: Sequoia 15.6

Steps to reproduce

1. Open a MM project with at least one non‑empty folder or create a new folder within the project and add file to this folder.
2. Right click on folder name and select "Open directory..."
3. Rename the folder to a new name, e.g. data_raw -> data_source.
4. Save and sync.
5. Refresh project in plugin.
6. Observe that both folders are available.
7. Inspect the “old” folder entry in the plugin tree: it is empty.

Actual results

• Duplicate folder entries (old empty + new correct) in the plugin tree after renaming a non‑empty folder and sync.
• Web dashboard reflects only the new folder (no duplicate).

Expected results

• After a folder rename, only the new folder should appear in the plugin tree.
• Old folder entry should be invalidated immediately without requiring restart.

Screenshots or logs

Conclusion
Created by GitHub Copilot and supervised by a human test analyst.

No source file or test is named. Start by reproducing the rename and sync in QGIS 3.40.5 with Mergin Maps plugin 2025.4.0, then trace how the plugin refreshes its project tree. Done means the renamed folder appears once and the old empty entry is invalidated without restarting.