Player gets stuck in a "Stopping" loop when entering Play mode with a Scenario using a Scene from a read-only package

Reproduction steps:
1. Create a new project
2. Install Multiplayer Play Mode package (Window > Package Management > Package Manager)
3. Open Play Mode Scenarios window (Window > Play Mode > Scenarios) and create a new Scenario
4. Add an additional Editor Instance and attach any Scene Asset that isn’t “SampleScene” (e.g. “Basic”) to the newly created Scenario
5. Select the newly created Scenario as the active Scenario and enter Play mode
6. Observe the Active Scenario window

Actual result: "Opening scene in read-only package!” pop-up appears and Player gets stuck in a “Stopping" loop
Expected result: Player stops cleanly

Reproducible with: 1.6.3 (6000.0.79f1), 2.0.2 (6000.3.20f1, 6000.5.4f1), 3.0.0 (6000.6.0b5, 6000.7.0a3)

Reproduced on: Ubuntu 24.04, macOS Tahoe 26.5 (M4)

Note: Players only get closed after changing the active Scenario