chore: add log assertions on IO #5089

Job	Run time
sbt plugin integration tests (ubuntu-latest)	4m 24s
sbt plugin integration tests (windows-latest)	7m 6s
Test Maven plugin	2m 7s
Mill plugin integration tests (ubuntu-latest)	3m 8s
Test on JDK 17 (windows-latest)	4m 51s
Test formatting	33s
Test on JDK 17 (ubuntu-latest)	3m 17s
Mill plugin integration tests (windows-latest)	4m 6s
Test on JDK 25 (windows-latest)	3m 49s
Test on JDK 25 (ubuntu-latest)	2m 34s
release	4m 38s
	40m 33s

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