- The owning top-level interface SessionEventMap must now be the SINGLE
EXPORTED declaration in @deepseek-ai/dsh-session: a non-exported local
interface (even inside the owning package) and a second exported copy
are hard errors, so a same-named helper can no longer be catalogued as
the on-disk vocabulary.
- Any SessionEventMap declaration carrying an extends clause is a hard
error: inherited keys join keyof SessionEventMap but have no catalog
row, so heritage is a silent-skip path the gate must reject.
Three new spec cases; RFC and module doc updated to match.