Follow seeks (scrub-while-paused) and add pauseAutoscroll/resumeAutoscroll

[maboa]

Resolves the core + pause-hook parts of #222. The scrollContainer constructor option is deferred to #217 (options-object refactor) where it belongs without further bloating the positional signature.

Changes

Core — follow seeks

BasePlayer.attachEventListeners now attaches a seeked listener that calls a new HyperaudioLite.handleSeeked() method. On every seek (including while paused) the transcript's read/unread visual state and scroll position re-align to the new playhead. The word-level .active class is not toggled here — that suppression-while-paused behaviour is tracked separately in #220.

This means scrubbing the media (drag the seek bar, jump in the native controls, set currentTime programmatically) now updates the transcript out of the box. Downstream consumers like the Hyperaudio Lite Editor that currently glue this themselves can drop their reimplementation.

The non-DOM player adapters (SoundCloud, YouTube, Vimeo, VideoJS) override attachEventListeners, so they're unaffected by this change. Adding seek-follow to each of those would be a sensible follow-up.

Pause hook

Two thin documented helpers:

player.pauseAutoscroll();   // e.g. while a user edits the transcript
player.resumeAutoscroll();

These wrap the existing instance.autoscroll boolean — no behaviour change, just a supported API instead of poking the field.

scrollContainer (deferred)

Adding scrollContainer as an 8th positional constructor argument would push the signature further into "boolean parameter trap" territory. Better landed alongside the options-object refactor in #217 — added a note there.

Compat

• Seeked listener: technically a behaviour change (scrub-while-paused now updates transcript instead of doing nothing), but the previous behaviour was the gap the issue is about. Consumers with their own glue will run twice harmlessly until they remove it.
• Pause/resume helpers: pure addition, zero risk.

Test plan

• npm test — all 25 Jest tests pass
• Manual: native <video> example — scrub while paused, confirm transcript scroll + read/unread state follow
• Manual: native <video> example — pauseAutoscroll() from console, scrub, confirm no scroll; resumeAutoscroll(), confirm scroll resumes