iris/android: composing text sync, tap-vs-swipe focus, composer rebuild, atlas reset on app-switch

Four fixes from Iris's phone report on the dc01f88 build, plus her same-day
follow-up on swipe-vs-tap:

- android/ime.rs: InputConnection now calls InputMethodManager.updateSelection
  after every edit (new update_ime_selection, called from after_input) -- Gboard
  was holding keystrokes back with nothing telling it the app's selection/
  composing region had moved, which read as "doesn't enter it until I hit
  space, doesn't move the caret". New unit tests in widget/text/edit.rs cover
  the buffer-level composing/commit/delete/selection operations directly.

- attr.rs: Selector/Selectable rewritten around a shared on_press dispatcher
  over PressStart/Pressing/PressEnd instead of click_or_drag(), so a field
  that isn't already focused only grants focus (and requests the IME) on a
  completed tap -- press and release with no frame past DRAG_SLOP. A drag
  is never consumed, so whatever is behind the field still sees it. New
  FocusHost::is_focused (both platform impls) and TextEdit::press_origin
  back this. Verified on the emulator: dumpsys input_method's mInputShown
  stays false after a swipe over the composer, true after a tap.

- iris_core: GlyphAtlas::clear()/Textures::reset(), called together from
  android/view.rs's surface_changed exactly when a genuinely new renderer is
  built (app-switch, not the keyboard-resize path that already reuses the
  renderer) -- both CPU-side caches otherwise kept pointing at the old,
  destroyed device's textures. Verified on the emulator: home, reopen, every
  glyph still on screen.

- transcript-ui/composer.rs: rebuilt as one widget (unchanged Stack{rect,
  span} idiom, capped at ~6 lines via MaxSize + .scrollable(), wrapped in one
  Pad whose bottom Composer::set_bottom_inset rewrites in place so the bar
  sits on the IME or nav-bar inset with no rebuild -- rebuilding would drop
  focus/selection/in-progress text). Wired from bench_client.rs's existing
  on_insets_changed.

A second, deeper bug found while verifying the composing fix is NOT fixed
this pass: composed text never becomes visible at all. A new layout_tests.rs
test proves the widget tree's own region math is correct across a keyboard
resize, ruling that out; RUST.md's P0 box has the full writeup and what to
check next (UiRenderState::redraw's single-widget path, or something
force-gles-specific -- this AVD has no Vulkan adapter to rule that out with).

cargo fmt/clippy/test --workspace and cargo ndk clippy all clean.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

iris/core/src/primitive/texture.rs

@@ -141,6 +141,27 @@ impl Textures {
         self.updates.push(Update::Patch(handle.slot, rect));
     }
 
+    /// Forget every image, page and pending update -- what a genuinely new
+    /// GPU device needs alongside [`crate::render::atlas::GlyphAtlas::
+    /// clear`], which this module's own doc references: every slot number
+    /// and every queued [`Update`] here describes the *old* device's
+    /// textures (an `Update::Push`/`Update::Patch` already drained into a
+    /// renderer that no longer exists is gone for good, and a fresh
+    /// `UiRenderNode`'s own texture manager starts with none of them
+    /// applied), so nothing is lost by starting this bookkeeping over too.
+    /// Any `TextureHandle` a caller still holds across the reset (none in
+    /// the transcript screen this reset is wired up for today -- confirmed
+    /// by grep, the only standalone (non-atlas) image anywhere in this
+    /// workspace is `iris/widget/image.rs`'s `Image`, used by the separate
+    /// `tabs-ui` example) is left pointing at a slot this instance no
+    /// longer recognises and needs reinserting via `add`/`add_page` again
+    /// -- the same pre-existing gap a renderer restart already left for
+    /// such a handle before this method existed, just named rather than
+    /// silent now.
+    pub fn reset(&mut self) {
+        *self = Self::new();
+    }
+
     pub fn free(&mut self) {
         for (kind, idx) in self.recv.try_iter() {
             self.images[idx as usize] = None;

iris/core/src/render/atlas.rs

@@ -173,6 +173,25 @@ impl GlyphAtlas {
     pub fn glyph_count(&self) -> usize {
         self.entries.len()
     }
+
+    /// Forget every page and every rasterised entry -- what a genuinely new
+    /// GPU device needs (`android::view::IrisViewPeer::surface_changed`'s
+    /// "not already live" branch, e.g. after backgrounding): the pages this
+    /// atlas remembers are `TextureHandle`s into the *old* device's
+    /// textures, which no longer exist, and every `GlyphEntry`'s `uv_min`/
+    /// `uv_max`/`layer` point into them. Without this, a glyph already
+    /// cached here is treated as "already placed" and never re-inserted
+    /// into the fresh (empty) atlas the new renderer actually has --
+    /// exactly the "rectangles stay, glyphs disappear" bug the resize path
+    /// (`AndroidRenderer::resize`) was built to avoid for the reuse case;
+    /// this is its counterpart for the case where the renderer really is
+    /// new. Dropping `pages` also drops its `TextureHandle`s, which send a
+    /// free message back through their `Textures`; see `Textures::reset`'s
+    /// doc for why that is harmless here.
+    pub fn clear(&mut self) {
+        self.pages.clear();
+        self.entries.clear();
+    }
 }
 
 fn fits(page: &Page, need_w: u32, need_h: u32) -> bool {