iris is the framework alone; the app is one crate in app-rust/

Iris: "the organization of the rust rewrite is a mess right now... there
shouldn't be anything related to the app inside of iris. Iris is supposed
to be the UI framework alone." And, on the crate count: "I'm confused why
the app only code needs more than one crate though."

Nine cargo workspaces become three, and the port's project code -- which
sat in five places, four of them inside the framework -- becomes one crate,
`ai-app`, in `app-rust/`:

  client-core                -> app-rust/src/client
  iris/transcript-ui         -> app-rust/src/ui
  iris/transcript-fixture    -> app-rust/src/ui/fixture.rs + tests/ + touch/
  iris/desktop-app           -> app-rust/src/desktop + src/bin_desktop.rs
  iris/android-app           -> app-rust/src/android + android-project/
  android-shell              -> app-rust/src/shell

iris/ keeps core, macro, the iris crate, tabs-ui and rig-input, and now
mentions no session, transcript, setup or server anywhere.

Only two of the old splits had a reason that survived reading. event-model
stays a crate at the repo root because server/ depends on it too, so a
crate is what makes the backend and the app agree by construction. The two
Android .so names looked like a hard constraint -- a package produces one
library artifact -- until P2 turned out to already plan merging those two
Android apps into one; both faces now come out of libai_app.so, picked
apart by features so `--no-default-features --features shell` keeps wgpu,
parley and iris out of the Compose app's APK. docs/RUST.md's "One app
crate" has the rest, including what each remaining feature is for.

DECISIONS.md and SUBAGENTS.md move into docs/ with everything else.

Verified: ./run-tests.sh and `cd iris && cargo test` green, clippy and fmt
clean in all five workspaces, `cargo ndk -t x86_64` links libai_app.so,
build-apk.sh produces an APK that installs and launches on this checkout's
emulator (Gl ... virgl, as expected), and the phone-sized headless
screenshot renders the transcript unchanged.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

core/src/widget/widgets.rs

@@ -11,6 +11,11 @@ pub struct Widgets {
     send: Sender<WidgetId>,
     recv: Receiver<WidgetId>,
     pub(crate) waiting: HashSet<WidgetId>,
+    /// Every widget that has ever been given an explicit `.label()` --
+    /// `ui::access::AccessTree` walks exactly this set, not the whole
+    /// arena, so a widget nobody named costs it nothing. Symmetric with
+    /// `free_next` below, which is this set's one removal path.
+    named: HashSet<WidgetId>,
 }
 
 impl Widgets {
@@ -20,6 +25,7 @@ impl Widgets {
             needs_redraw: Default::default(),
             vec: Default::default(),
             waiting: Default::default(),
+            named: Default::default(),
             send,
             recv,
         }
@@ -95,9 +101,20 @@ impl Widgets {
         &self.data(id.id()).unwrap().label
     }
 
-    /// useful for debugging
+    /// Also the one place a widget opts into `ui::access`'s AccessKit tree
+    /// (RUST.md's I4) -- see `named`'s doc comment.
     pub fn set_label(&mut self, id: impl IdLike, label: String) {
-        self.data_mut(id.id()).unwrap().label = label;
+        let id = id.id();
+        self.data_mut(id).unwrap().label = label;
+        self.named.insert(id);
+    }
+
+    /// Every widget with an explicit name, for `ui::access::AccessTree` to
+    /// walk. Order is unspecified; `AccessTree` doesn't need one; a screen
+    /// reader's own traversal is worked out by uiautomator from each
+    /// node's on-screen bounds instead.
+    pub fn named(&self) -> impl Iterator<Item = WidgetId> + '_ {
+        self.named.iter().copied()
     }
 
     pub fn data_mut(&mut self, id: impl IdLike) -> Option<&mut WidgetData> {
@@ -107,6 +124,7 @@ impl Widgets {
     pub fn free_next(&mut self) -> Option<WidgetId> {
         let next = self.recv.try_recv().ok()?;
         self.vec.free(next);
+        self.named.remove(&next);
         Some(next)
     }