[wieslawsoltes]

Problem

Finite CSS keyframe animations advanced visually but did not dispatch their terminal animationend event. VS Code's language-status icon removes its finite wiggle class from that event, so the missing event could retain visible frame demand after the animation completed.

Change

• Retain and dispatch a browser-shaped finite animationend record with animationName, elapsedTime, pseudoElement, bubbles, and cancelable.
• Preserve the animation start timestamp across an unrelated recascade and dispatch the terminal event exactly once.
• Allow the event listener to remove the triggering class and release host frame demand.
• Keep the uncommon event queue lazy through unique_ptr; the existing 384-byte native_document static footprint gate remains intact.
• Add a product-neutral WPT contract and component-profile coverage.

Focused validation

• Release native engine with real V8, html5ever, cssparser, Servo selectors, generated WebIDL bindings, and graphics: built successfully.
• finite-keyframe-animation-end: 25/25 focused passes.
• css-animation-end-class-removal.html: 1/1 document and 1/1 subtest passed against the rebuilt native engine.
• The cumulative stack gate animation-logical-inset-isolation: 50/50 passes.
• git diff --check: passed.

Closes #113.

Stack

1. Dispatch finite CSS animation events #119 — animation lifecycle and lazy event queue
2. Isolate logical inset transition test time #122 — cumulative logical-inset timeline isolation

Native GitHub Stack #190. Validate and merge from the cumulative top.