docs: collect the three breaking fixes into one queued section

They were living in code comments at their sites, which is where the person
fixing them looks and not where the person planning a release looks.

Also corrects a fabricated zero found while writing it: RamInfo::shared is 0
on macOS because simon does not read it, not because the machine shares
nothing. It sat uncommented directly below a carefully justified
`buffers: 0`, which is genuinely a fact about the platform. No ontology
entity surfaces `shared`, so no agent is misled — a library caller reading
MemoryStats is.

All three queued items are the same fault: a type with no way to say "not
read", so absence is encoded as zero and stops being distinguishable from a
measurement of zero. That is the distinction this crate exists to preserve,
and these places cannot preserve it without an API change. Hence one section
rather than three scattered notes: it is one change of principle applied in
three places, and doing them together is what makes the principle legible.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>