Organize Iris support files

docs/LAYOUT.md

@@ -244,8 +244,7 @@ have `ActiveData`'s existing lifecycle through `remove`/`remove_rec`.
 ## Density: `Len::dp`, resolved at `apply_rest` time
 
 Iris asked for a third length kind beside `abs` (physical pixels) and
-`rel`/`rest` (a fraction of the parent) — IRIS_TODO.md's "density-
-independent length unit" — after the P0 phone pass found 16px text
+`rel`/`rest` (a fraction of the parent) after the P0 phone pass found 16px text
 drawing at roughly a third size on a real phone. The fix that shipped
 first (RUST.md's P0 box) was a global stopgap: divide the whole window
 into a "logical" coordinate space (physical ÷ `content_scale`) and let