I have read that this piyut was intended to be recited on Shabbat Hagadol. Where does it first appear? Who wrote it?
These lines are the conclusion of one of the piyyutim for Shabbat HaGadol, composed by R. Joseph b. Samuel Bonfils (Tuv 'Elem) (11th century CE) and recited in Minhag Ashkenaz during chazarat hashatz of shacharit.
To quote from the above-linked Wikipedia page:
Of his many piyyuṭim, the best-known is that written for "Shabbat HaGadol" (the Sabbath before Passover), beginning with the words "Elohei haruchot," and containing the rules for the Passover-cleaning ("bi'ur") and the narrative service for the evening. Its concluding lines, beginning with "Hasal seder pesach", appear near the end of the Passover Haggadah.
It is ascribed to רב יוסף טוב עלם as can be seen in the articles below with the Hebrew Wikipedia articles containing more extensive information.
https://he.wikipedia.org/wiki/אבוא_בחיל_להתיצבה (Chasal Sidur Pesach appears as the finale of this larger piyut)
Perhaps further examination of the sources in these articles will mention where the piyut first appeared.