She asked whether `masked_by` earns its place, since
`.background(x).masked()` looks like the same thing. Measured: for a
square-cornered surface it is (identical to the pixel on the composer at
the phone's size and density), and what the pair cannot express is a
clip that is not a box, which is why the method stands for now.
Her suggestion, in IRIS_TODO.md's "Reconsider": let `Stack` name where
its mask comes from the way `StackSize::Child(n)` already names where
its size comes from, at which point `masked_by` and `Masked::shape` both
go away.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
irisandClaude Opus 5
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