C-only edge lab

# Flow content lift

A/B are removed. This page stress-tests the C strategy against nested layouts, component anatomy, mixed direct content, data-heavy widgets, and pathological wrapper depth.

visible block cropped group component internal

The invariant gate is stricter than the visual preview: no node can be both block/group/internal, and no visible block can contain another visible block. A failing case means the inference boundary is not editor-safe.

Current read: if these cases stay green, the next real architecture move is not a `<Block>` tag. It is a core AST analysis pass that emits derived interaction units for hover, selection, drag handles, and drop indicators.