لَمْ يَكْتُبْ ← اُكْتُبْ
The jussive yaktub has final sukūn; the direct imperative uktub is built on sukūn. Same surface ending, different grammatical classification.
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Sound-Final: Built on Sukūn
The Imperative: Definition, Formation, Hamza, and Building Signs
لَمْ يَكْتُبْ ← اُكْتُبْ
The jussive yaktub has final sukūn; the direct imperative uktub is built on sukūn. Same surface ending, different grammatical classification.