* fix(frontend): stop stalled subtask pagination without losing steps
* docs(frontend): note the non-advancing page stop in the subtask backfill
The AGENTS.md backfill sentence only said the loop pages until a short page. It also stops on a full page that fails to advance the after_seq cursor, so record that stop condition as well.
The file sits at 49,149 of its 49,152-byte hard limit, so this is the minimal wording change that fits.
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Co-authored-by: TYY-2005 <334029581+TYY-2005@users.noreply.github.com>