How to reproduce:
1. Open the attached project "GridMarginRepro"
2. In the "MarginRepro" scene, enter Play mode
3. Observe the results
Expected results: Both boxes resolve to a height of 150px and stop at the white rule that marks the declared height, because "layout" is the border box and an element's own margin is not part of it
Actual results: The "display: grid" box resolves to 180px and visibly overshoots the rule by exactly its own 30px bottom margin, and its "grid-template-rows: 1fr" child is stretched to 180px, while the "display: flex" control correctly resolves to 150px
Reproducible with: 6000.7.0a5
Can't test with: 6000.0.81f1, 6000.5.9f1, 6000.6.0b9, 6000.7.0a4 (No feature)
Reproducible on: macOS Tahoe 26.6 (M1 Max)
Not reproducible on: No other environment tested