SUI 0.4.1

This release adds observable background tasks, makes reactive updates and text
rendering cheaper, improves platform font rendering, and adds touch scroll
inertia.

Highlights

• Added Task, TaskState, and TaskHandle for background work with progress,
  results, errors, and stale-worker protection. refresh keeps the previous
  result visible while loading, cancellation restores it, and TaskHandle::run
  completes the task from a future on the application's executor.
• Added batch to coalesce notifications, combine and combine_named to
  derive values from two to four observables, and changed().await to wait for
  a signal, task, or other observable to change.
• Added borrowed signal reads and in-place updates with with, modify, and
  mark_changed, plus pointer-compared and copy-on-write Arc updates with
  set_arc and modify_arc. Selector clones share one source subscription
  and a cached result, avoiding repeated work for multiple observers.
• Skipped clipped glyphs before rasterization and split grayscale masks from
  color and LCD glyphs. A grayscale atlas page now uses 4 MiB of GPU memory
  instead of 16 MiB each on the CPU and GPU; only pending uploads keep CPU
  pixels. Clipping also preserves tall marks and bitmap emoji at line edges.
• Followed Windows ClearType and Linux fontconfig/Xft smoothing preferences,
  improved Linux and Android slight hinting and coverage, and loaded Android
  system fonts with bundled fallbacks. Runtime text-policy changes now update
  retained text correctly.
• Added coasting touch scrolling to ScrollView and VirtualScrollView.
  Both expose on_offset_change and on_offset_change_with_ctx for wheel,
  keyboard, touch, fling, scroll bar, and programmatic moves. The widget book's
  navigation follows flings and keeps the selected entry after a jump.

Other changes

• Fixed open contours rendering as fans on Adreno 740 under Chrome's Vulkan
  WebGPU backend and made tooltip borders continuous around their tails.
• Kept menu and context-menu keyboard shortcuts on one line so long
  combinations stay aligned and vertically centered.
• Added download progress while the web demo loads its Wasm module and fonts,
  with startup errors displayed on the loading screen.
• Made Chrome text comparisons match the requested grayscale or LCD mode,
  added aggregate ink and alignment diagnostics, and added a light/dark,
  scale, and antialiasing comparison matrix.
• Fixed concurrent selector updates losing changes and reactive diagnostics
  recording older versions when notifications arrive out of order.
• Updated accessibility, Python, Node, Wasm, and Linux dependencies.

Compatibility and release notes

• Update the SUI crates together to 0.4.1. sinomo-ui-lucide remains at
  1.47.1, with the same bundled Lucide 1.47.0 icons.
• Selector closures now read signal values while the source is locked; they
  must not write to that signal. Debug builds report same-signal reentrant
  writes with a named panic instead of deadlocking. Observers still run
  synchronously on the writing thread; batching defers them until the batch
  ends on that thread.
• Rust 1.90 remains the minimum supported version. Browser support remains
  alpha, Android remains experimental, and Python and JavaScript bindings
  remain source-built and are not part of the registry release.