* fix(cli): check passes a still title card whose timeline follows the seek
* fix(cli): check warns on a still frame and fails only when an animation is stuck
* fix(cli): count a seek clock once per sample and point the error at the registered timeline
* fix(cli): judge a finished animation by its own completion state, not its end time
* test(cli): pin a Web Animation paused at its end as finished
* fix(cli): judge a reversed animation's end in its own direction, and read plain timelines
* test(cli): pin a plain timeline held at its end as finished
* test(cli): keep an unfinished plain timeline beside the finished one
* fix(cli): skip a timeline whose time cannot be read instead of calling it stuck
* fix(cli): skip an animation whose time is not a plain number, such as a scroll-driven one
* fix(cli): a partial timeline with plain values no longer stops the browser checks