Add retained paints and shared text selection

docs/IRIS_TODO.md

@@ -2,35 +2,10 @@
 
 Only open Iris framework work lives here. Delete an item when it lands.
 
-## Fix
-
-- [ ] **Colours are not in a defined colour space. Fix this before a
-  styling pass.** Both render backends prefer an sRGB surface
-  (`default/render.rs` and `android/render.rs`), while `fs_main` returns
-  `unpack4x8unorm` palette and image bytes unchanged. An sRGB attachment
-  treats those values as linear and encodes them again: Mocha Crust
-  (17,17,27) became (73,73,91) in a desktop screenshot measured on
-  2026-09-06.
-
-  Neither diagnostics nor startup logging records Android's selected surface
-  format. A device exposing only a non-sRGB surface can hide the shared bug.
-
-  Done means defining one convention for palette bytes, decoded images,
-  colour emoji and the clear colour, then converting exactly once for the
-  selected target. Record the selected format in diagnostics, and add a GPU
-  test that draws known non-black, non-white pixels into an sRGB target and
-  reads the stored bytes back; screenshots from desktop and Android then
-  confirm the same Catppuccin values rather than serving as the definition.
-
 ## Build (for the port)
 
 Framework capabilities needed by `RUST.md`'s port plan:
 
-- [ ] **Selectable, read-only text.** P0's report and P1's transcript rows
-  use `TextEdit` because `Selectable` is implemented only for it. That
-  makes prose focusable and opens the IME over text that cannot be edited.
-  A display widget needs the same selection geometry and clipboard path
-  without a text-input accessibility role or keyboard focus.
 - [ ] **Overflow ellipsis with an explicit retained end.** `TextAttrs` can
   only wrap or clip, so a tool summary is cut with no mark. Parley has no
   ellipsis primitive; use its line breaker to find the cut, but keep source
@@ -52,9 +27,9 @@ Framework capabilities needed by `RUST.md`'s port plan:
 - [ ] **Per-range backgrounds for rich text.** (**P1**.) Inline code is
   already monospace and coloured, but matching Compose's chip also needs
   the glyph run's boxes so a surface can be drawn behind exactly that byte
-  range. `TextEdit` already computes the same geometry internally for its
-  selection highlight; expose one shared primitive rather than giving the
-  app a second text-layout path.
+  range. The shared `TextSelection` engine already computes the same geometry
+  for selection highlights; expose one shared primitive rather than giving
+  the app a second text-layout path.
 - [ ] **A modal/dialog primitive.** (**P1**, reused by **P3** and
   **P5**.) Needed for the session settings dialog, `UsageDialog`'s
   equivalent, and the delete-with-`deleteForeign` confirmation with its
@@ -69,6 +44,14 @@ Framework capabilities needed by `RUST.md`'s port plan:
 
 ## Later
 
+- [ ] **Intern independently constructed solid paint definitions.** Inline
+  `rect(Srgba8::...)` values currently receive a new `PaintId` each time.
+  Cache them by canonical linear RGBA bits, but keep `Paints::add` explicitly
+  unique so two semantic theme roles that start with the same value can later
+  change independently. Cache entries must be weak and disappear when the
+  last real handle releases the slot; gradients and texture paints need their
+  own identity rules rather than inheriting solid-value interning blindly.
+
 - [ ] **Property/content animations.** Cosmetic, so after correctness and
   parity. Keep them modular, like input; scrolling already animates through
   `Widget::tick` and `UiData::animate`. A widget that does not opt in must
@@ -85,8 +68,8 @@ Framework capabilities needed by `RUST.md`'s port plan:
   against `.masked_by(rect(BAR_FILL))` on the composer at the phone's own
   size and density and the two are identical to the pixel. What the pair
   cannot express is a clip that is not a box: `Painter::set_mask` writes
-  a `RectPrimitive::color(Color::NONE)` at the widget's own region, with
-  no radius, so `.background(rect(fill).radius(r)).masked()` draws a
+  a `RectPrimitive::color` using `PaintId::NONE` at the widget's own region,
+  with no radius, so `.background(rect(fill).radius(r)).masked()` draws a
   rounded panel and then cuts its content square. Both other call sites
   (`row.rs`'s fence, `tool.rs`'s raw output) are rounded, which is why
   the method stands for now.