iris: move text state into shared resources

docs/LAYOUT.md

@@ -279,9 +279,9 @@ rasteriser (`TextData::place`, which reads back whatever `shape` set) is
 the display's *physical* size, and the glyph atlas holds a bitmap at the
 resolution it is actually shown at. `GlyphKey.size` already keys on the
 resolved size, so a cache entry is naturally per-physical-size with no
-further change. The one caller with no `Painter` to read density from
-(`TextEditCtx::layout`, cursor movement and hit-testing) reads a second
-copy kept directly on `TextData` (`TextData::density`) instead — an
+further change. The callers with no `Painter` to read density from (cursor
+movement and hit-testing through `TextHandle::layout`) read a second copy kept
+directly on `TextData` (`TextData::density`) instead — an
 accepted duplication rather than threading a `Painter` into every input
 handler for one field, the same tradeoff `AndroidRenderer::content_scale`
 already makes for the Diagnostics page.