Hard caps on a hand-edited or corrupt store, so it can never flood the
break overlay or blow the read budget. Mirrors the defensive count/length
limits the content-pack path applies to plugin-supplied idea lists.
Trim, drop blank lines, and cap a user-entered chore list to the store’s
limits. Pure so the set_chores command and any future import path share
one definition of “a valid list”: each item is trimmed and truncated to
MAX_CHORE_LEN characters, blanks are removed, and at most
MAX_CHORE_ITEMS survive.