The SUBJECT-ENTRY RULE: the subject-kind entry is what makes a definition
"about" a subject document — the kind is the discriminator, never a
heuristic over required refs. One predicate shared by applicability's type
matching (acceptsDocumentType), the autonomous-start deploy invariant,
and the root-read deploy check (a root-reading start.filter needs a
subject entry to bind a candidate root) — so "counts as a subject" can't
drift between them.
The SUBJECT-ENTRY RULE: the
subject-kind entry is what makes a definition "about" a subject document — the kind is the discriminator, never a heuristic over required refs. One predicate shared by applicability's type matching (acceptsDocumentType), the autonomous-start deploy invariant, and the root-read deploy check (a root-readingstart.filterneeds a subject entry to bind a candidate root) — so "counts as a subject" can't drift between them.