Add very basic Animation support

[NoahR02]

This adds basic animation support and adds an example of how to use the api.

Currently font properties won't animate because the layout logic is being done in update_state rather than compute_layout.

[Copilot]

Pull Request Overview

Adds foundational animation support across the core UI library and a new example demonstrating how to use it.

• Introduce Animation, KeyFrame, LoopAmount, and TimingFunction types for defining animations.
• Extend Style, Element, and the rendering loop (App/CraftWinitState) to drive animations each frame.
• Add examples/animations as a working demo of the new API.

Reviewed Changes

Copilot reviewed 15 out of 16 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
website/src/examples.rs	Register the new "Animations" example in the sidebar
examples/animations/main.rs	Provide a basic animation demonstration
examples/animations/Cargo.toml	Setup dependencies for the animations example
crates/craft_core/src/style/styles.rs	Add animations field and accessor/mutator methods
crates/craft_core/src/reactive/reactive_tree.rs	Store previous animation flags in ReactiveTree
crates/craft_core/src/lib.rs	Expose the animations module and init flags/time
crates/craft_core/src/elements/element_styles.rs	Add push_animation builder method
crates/craft_core/src/elements/element_states.rs	Derive Hash for ElementState enum
crates/craft_core/src/elements/element.rs	Implement on_animation_frame and reset_layout_item
crates/craft_core/src/elements/base_element_state.rs	Track per-element active animations
crates/craft_core/src/craft_winit_state.rs	Switch event loop to Poll when animations active
crates/craft_core/src/app.rs	Integrate animate_tree into the main update/render loop
crates/craft_core/src/animations/mod.rs	New animations module exports
crates/craft_core/src/animations/animation.rs	Define animation primitives and interpolation logic
Cargo.toml	Add examples/animations to the workspace

Comments suppressed due to low confidence (1)

crates/craft_core/src/style/styles.rs:466

• This public method lacks documentation. Please add a doc comment explaining its behavior—e.g., that it retrieves a named Animation if set in the style.

    pub fn animation(&self, animation: &str) -> Option<&Animation> {

[Copilot]

Clearing animations on every merge will drop scheduled animations as soon as you interpolate once. Consider preserving or merging the existing animations list instead of resetting it.

Suggested change

	merged.animations = None;
	merged.animations = match (&old.animations, &new.animations) {
	(Some(old_animations), Some(new_animations)) => {
	Some(old_animations.iter().chain(new_animations.iter()).cloned().collect())
	}
	(Some(old_animations), None) => Some(old_animations.clone()),
	(None, Some(new_animations)) => Some(new_animations.clone()),
	(None, None) => None,
	};

[Copilot]

[nitpick] Allocating and sorting a Vec of keyframes on every frame may be inefficient. You could keep keyframes pre-sorted in the Animation struct or use a fixed-size buffer to avoid repeated heap allocations.

Suggested change

	let mut sorted = animation.key_frames.iter().collect::<Vec<_>>();
	sorted.sort_by(|a, b| a.offset_percentage.total_cmp(&b.offset_percentage));
	for window in sorted.windows(2) {
	for window in animation.key_frames.windows(2) {