Great question. I think Rashi gives two answers to what is the ויכל אלקים ביום השביעי which answer your question.
And God completed on the seventh day: Rabbi Shimon said: [A human
being of] flesh and blood, who cannot [exactly] know his times and his
moments, must add from the profane to the holy [i.e., he must add some
time to the Sabbath.] The Holy One, blessed be He, Who knows His times
and His moments [exactly], entered it [the Sabbath] within a
hairbreadth, and it therefore appeared as if He completed it [His
work] on that day. Another explanation: What was the world lacking?
Rest. The Sabbath came, and so came rest. The work was completed and
finished. — [from Gen. Rabbah 10:9]
וַיְכַל אֱלֹהִים בַּיּוֹם הַשְּׁבִיעִי: ר' שִׁמְעוֹן אוֹמֵר בָּשָׂר
וָדָם, שֶׁאֵינוֹ יוֹדֵעַ עִתָּיו וּרְגָעָיו צָרִיך לְהוֹסִיף מֵחֹל עַל
הַקֹּדֶשׁ, הַקָּדוֹשׁ בָּרוּךְ הוּא שֶׁיּוֹדֵעַ עִתָּיו וּרְגָעָיו,
נִכְנָס בֹּו כְּחוּט הַשַּׂעֲרָה, וְנִרְאֶה כְאִלּוּ כִלָּה בוֹ
בַיֹּום. דָּבָר אַחֵר מֶה הָיָה הָעוֹלָם חָסֵר? מְנוּחָה, בָּאת
שַׁבָּת בָּאת מְנוּחָה, כָּלְתָה וְנִגְמְרָה הַמְּלָאכָה:[1]
Answer #1 the first מלאכתו is in reference to the מלאכה that was just done has been immediately ceased, but the second is that no מלאכה of any kind was done from then on either.
Answer #2 one cessation is in reference to the previous work and one cessation is in reference to "creating" מנוחה
Although I don't think the אור החיים הקדוש is saying the exact same thing, he does make mention of the nuance between different forms of creation. Like what was just being done just before shabbos and all the other creation that was done during the full six days. I personally see this implied by Rashi and his divrei hamaskil, but certainly can be argued with.
