Draw GBuffer pass appears black in Frame Debugger when Deferred or Deferred+ is enabled

Reproduction Steps
1. Open the project
2. Open Assets/Scenes/Sample Scene.unity
3. Open the Frame Debugger
4. Enable the Frame Debugger and select the "Draw GBuffer" pass
5. Observe the Game view

Actual results: The Output displays a completely black texture
Expected results: The Output displays a cube texture on a black/blue background

Reproducible with: 6000.3.5f1, 6000.4.0b5, 6000.5.0a2, 6000.5.0a5
Not reproducible with: 6000.0.66f1, 6000.5.0a1

Reproducible on: macOS 26.2 Editor
Not reproducible on: Windows Editor

Note: When creating a new project, SSAO is enabled by default. In that case, SSAO runs after the Draw GBuffer pass, which prevents pass merging, so the issue does not occur in a default new project unless SSAO is disabled.