v0.8.2

fix: add destroyed flag to prevent all post-destroy errors

GraphState gains a `destroyed: bool` field. Set to true in destroy()
before cleanup. All event handlers, ResizeObserver, animation loop,
and redraw_with_time check this flag and bail immediately if true.

This prevents the cascade of 'Cannot set width', 'getBoundingClientRect
of undefined', and RefCell panics that occur when React StrictMode
destroys and remounts the component.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>