clang-format 18 wraps the family label and the glyph x offset differently from
the local clang-format 23. The preview test takes the CI output so the bottom
of the stack passes the style job on its own.
The PR showed one theme's badge and sticker sheets, which cannot show that the
filled treatments read on every palette. Each shipped theme and scheme now
gets its own sheet: both semantic families, three glyphs, as line glyphs,
stickers and badges, at 16 and 24 px, on the window and button surfaces the
contrast is measured against, with the disabled fallback under each family.
The generator lives in its own test file so the preview work does not have to
move the branches above it.
