The previous round of SAFETY doc additions used the generic comment
'// SAFETY: caller must verify the safety contract for this operation'
which was vague and added no information beyond the unsafe keyword.
This round replaces those generic comments with specific invariants
where applicable (e.g. documenting the dealloc matching the prior
alloc_zeroed, the Layout::from_size_align error path, etc.).
Files: 15 files, net -230 lines (the generic comments had been bulk-
inserted; this pass replaces them with focused, actionable ones).
vasilito
b295b80882