HeadlessFrame

An immutable, thread-safe result of one synchronous headless render.

The frame retains the physical image and a detached, read-only snapshot of logical semantics. Semantics are in core emission order, remain unscaled and unclipped, and no description, tree, or command list is retained. The image size is exactly the checked logical viewport multiplied by pixelScale. All exposed frame, image, and semantics reads are safe from any thread after construction.