fix(ontology): two more non-nullable entities that a VM resolves absent

CI found `board.input.{n}.interface` and `memory.bandwidth.generation`
declared non-nullable while their readers return `Unknown` on both runners. A
virtualised input device reports no interface the classification recognises,
and a VM's SMBIOS routinely names no memory generation. Both resolve on bare
metal, which is why the local suite passed.

The gap this exposes is not the one already recorded. macOS passed and the two
failures were on different operating systems, so it is not a platform gap --
it is a *hardware* gap. CI runners are virtual machines and this desktop is
not, and no cross-target check would have found it, because the code compiles
identically either way and only the readings differ.

Seven nullability violations have now come out of this batch, every one the
same shape: an entity declared non-nullable whose reader has a legitimate
`Unknown`. The absence-word guard converts those honestly; the declarations
never followed.

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