iris: I4 -- accessibility names via AccessKit

Builds one flat AccessKit tree (iris_core::ui::access::AccessTree) from
iris's own widget tree: a synthetic Role::Window root with every named
widget as a direct child, names from the existing `.label()`, roles from
a new Widget::access_role() (default Unknown, TextEdit overrides to
TextInput/MultilineTextInput), bounds from UiRenderState::window_region
so a moved subtree reports where it actually is. Modular the way input's
sense registry is: Widgets gained one HashSet<WidgetId> ("named"),
populated only by .label()/set_label and drained by free_next (the
existing removal path), and AccessTree walks only that set -- a widget
nobody named costs it nothing. Updates only when the named set's name,
role or bounds actually changed, with a rebuild counter mirroring
take_counters (confirmed 1/0/1 across first-draw/unchanged/moved in
access_tests.rs).

Pushed through accesskit_winit on the desktop (DefaultApp::new now
creates the window hidden, builds the adapter, then shows it, per that
constructor's requirement) and accesskit_android on Android
(IrisViewPeer now implements AccessibilityNodeProvider). Both action
handlers are inert on purpose: AGENTS.md's tap-by-name is a real touch
at the node's bounds, not an AccessKit action request, so the ordinary
pointer path already answers it once bounds are right. E1's
detach-abort mitigation is carried into android/access.rs's
raise_if_enabled, which gates every QueuedEvents::raise on
AccessibilityManager.isEnabled().

tabs-ui's five switch buttons now carry .label()s matching their
on-screen text, giving both the desktop run and the emulator step real
names to find.

Verified on host: cargo fmt/build/clippy/test all clean (28 tests, 3
new), cargo ndk build+clippy clean for iris and iris-android-app,
run-headless.sh tabs --shot byte-identical to I2's prior screenshot
(27266 bytes). Not run: the emulator step (ui-trace tap-by-name against
iris-android-app), held by another session this pass -- exact commands
recorded in RUST.md's I4 box.

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

iris/Cargo.toml

@@ -13,6 +13,7 @@ swash = { workspace = true }
 pollster = { workspace = true }
 wgpu = { workspace = true }
 image = { workspace = true }
+accesskit = { workspace = true }
 tokio = { workspace = true, features = ["sync", "rt", "rt-multi-thread"] }
 
 # winit everywhere except Android; android-view (below) is what stands in
@@ -27,6 +28,11 @@ tokio = { workspace = true, features = ["sync", "rt", "rt-multi-thread"] }
 [target.'cfg(not(target_os = "android"))'.dependencies]
 winit = { workspace = true }
 arboard = { workspace = true, features = ["wayland-data-control"] }
+# I4 (RUST.md): the desktop half of the AccessKit push, `winit`'s own
+# adapter over `accesskit`. No pin needed the way android-view's rev is
+# pinned -- this is an ordinary crates.io release with no local abort to
+# track (that finding is Android-only, see below).
+accesskit_winit = "0.34.0"
 
 # Pinned to the exact commit RUST.md's E1 (2026-09-04) measured on this
 # emulator -- real Vulkan rendering, a working `InputConnection`, and the
@@ -35,6 +41,14 @@ arboard = { workspace = true, features = ["wayland-data-control"] }
 # is dated rather than floating.
 [target.'cfg(target_os = "android")'.dependencies]
 android-view = { git = "https://github.com/rust-mobile/android-view.git", rev = "bec6c62a96cef8239b0fd7fedeef9b184d02e3a1" }
+# I4 (RUST.md): the Android half of the AccessKit push, over android-view's
+# `AccessibilityNodeProvider`. **0.8.0 carries the same detach-abort E1
+# found on 0.4.0** (the `State` enum still never returns to `Inactive`,
+# and `send_completed_event` still unwraps a Java exception) -- advancing
+# the version is not the fix, so pinning to a specific rev buys nothing
+# here the way it does for android-view itself. `android/view.rs`'s
+# `raise_if_enabled` is the mitigation, carried from E1.
+accesskit_android = "0.8.0"
 # Not re-exported by android-view (only `jni` and `ndk` are), and needed
 # for `android/insets.rs`'s own id -> state map -- the same reason
 # android-view's own `PEER_MAP` carries one.
@@ -82,6 +96,7 @@ parley = "0.11.1"
 swash = "0.2.10"
 fxhash = "0.2.1"
 arboard = "3.6.1"
+accesskit = "0.25.0"
 iris-core = { path = "core" }
 iris-macro = { path = "macro" }
 tokio = "1.49.0"