docs: tick closed P0s in the release-readiness checklist (status upda… #5

Job	Run time
Opt-in lane (2025-11-25)	4m 48s
Spec mutex (both features must not compile)	23s
Rustdoc (deny warnings)	1m 13s
Default lane (2026-07-28)	4m 48s
	11m 12s

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