refactor: Move live dataset paging into DatasetClient.iterateItems

[vdusek]

Moves the live paging behind RunClient.iterateDatasetItems() (#1085) into a new DatasetClient.iterateItems(). Without stopCondition, it iterates like listItems(). With it, the iterator follows a dataset that is still being written to: stopCondition is called before each poll, resolves to whether the writer has finished, and paces the polls. It can't be combined with desc.

iterateDatasetItems() keeps its options and sends the same requests. It now only pins the run on a lastRun() client and passes a callback that long-polls waitForFinish(). The dataset client does the paging: pages end at itemCount, the rows past the lagging itemCount are read once the run finishes, and a limit=1 read checks a page that filters emptied.

This follows Pijukatel's review on the Python twin, apify/apify-client-python#1079, which got the same change in apify/apify-client-python@fbf4192. It keeps the dataset paging in the dataset client and leaves only the end condition in the run client.

✍️ Drafted by Claude Code

[github-actions]

⚠️ There are broken links in the documentation.

See more at https://github.com/apify/apify-client-js/actions/runs/37437325785#summary-112182231331

[vdusek]

Closing: per Pijukatel's review on the Python twin, we're not adding the public stopCondition argument. The paging stays in RunClient.iterateDatasetItems (#1085) and can be refactored later if needed.

✍️ Drafted by Claude Code