add Thaum.app and SomeApp.run quick-start entry points

[phaedryx]

A little sugar to make things a bit more approachable

[Copilot]

Pull request overview

This PR adds quick-start entry points to make bootstrapping a Thaum app more ergonomic: Thaum.app { … } for anonymous apps and SomeApp.run for classes that include Thaum::App.

Changes:

• Add Thaum::App::ClassMethods#run and auto-extend it on include Thaum::App.
• Add Thaum.app(**, &block) to build an anonymous app class from a block and run it (with a missing-block guard).
• Update README, examples, changelog, and add a focused test for the new entry points.

Reviewed changes

Copilot reviewed 21 out of 21 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/test_app_dsl.rb	Adds coverage for .run being added by include Thaum::App and for Thaum.app requiring a block.
README.md	Documents Thaum.app quick-start and updates usage to prefer SomeApp.run.
lib/thaum/app.rb	Extends including classes with a .run class method that instantiates and delegates to Thaum.run.
lib/thaum.rb	Adds Thaum.app helper that builds an anonymous Thaum::App class from a block and runs it.
examples/hello_world.rb	Switches the “Hello World” example to use Thaum.app do … end.
examples/counter.rb	Uses CounterApp.run instead of Thaum.run(CounterApp.new).
examples/checkbox.rb	Uses CheckboxApp.run instead of Thaum.run(CheckboxApp.new).
examples/layout_demo.rb	Uses LayoutDemoApp.run instead of Thaum.run(LayoutDemoApp.new).
examples/log_generator.rb	Uses LogGeneratorApp.run(...) instead of Thaum.run(LogGeneratorApp.new, ...).
examples/modal.rb	Uses ModalApp.run instead of Thaum.run(ModalApp.new).
examples/mouse.rb	Uses MouseApp.run instead of Thaum.run(MouseApp.new).
examples/progress_bar.rb	Uses ProgressApp.run instead of Thaum.run(ProgressApp.new).
examples/scroll_view.rb	Uses ScrollViewApp.run instead of Thaum.run(ScrollViewApp.new).
examples/spinner.rb	Uses SpinnerApp.run instead of Thaum.run(SpinnerApp.new).
examples/status_bar.rb	Uses StatusBarApp.run instead of Thaum.run(StatusBarApp.new).
examples/stopwatch.rb	Uses StopwatchApp.run(tick: ...) instead of Thaum.run(StopwatchApp.new, tick: ...).
examples/tabs.rb	Uses TabsApp.run instead of Thaum.run(TabsApp.new).
examples/text.rb	Uses TextApp.run instead of Thaum.run(TextApp.new).
examples/theme_picker.rb	Uses ThemePickerApp.run instead of Thaum.run(ThemePickerApp.new).
examples/todo.rb	Uses TodoApp.run instead of Thaum.run(TodoApp.new).
CHANGELOG.md	Notes the new Thaum.app / SomeApp.run entry points and guidance on when to still use Thaum.run(app).

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