docs: the spacing rules — blocks, the label row, wells carved inside their rect

cce-ui@f7592ea; no code change, the exhibits follow the strategies.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

 README.md | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 9b46ef0..a912ca7 100644
--- a/README.md
+++ b/README.md
@@ -48,8 +48,11 @@ their default spacing (`layout::CONTROL_GAP`, one control height, the one gap
 every strategy and row builder uses in both axes), so what you see is what a
 container using that strategy does: a strategy places controls' CONTENT boxes,
 a detached label hangs in the gap above its control, mixed labeled and
-unlabeled controls line up by content, and every detached label sits at the
-same `DETACHED_LABEL_INSET`. The exhibit
+unlabeled controls line up by content (a strategy reserves the label row for
+every child of a labeled container), every detached label sits at the same
+`DETACHED_LABEL_INSET`, and every well, trough and raised plateau is carved
+inside its widget's rect (`layout::carve_inside`) so a widget's footprint is
+its rect. The exhibit
 area below the dropdown scrolls (wheel, or the scrollbar at its right edge)
 when a layout runs past the window. `Color Ramp...` and `Ramp...` open the
 ColorRamp and Ramp editors in their own child windows.