Set when the live read itself failed. Clears when the stream recovers.
True only while the observer snapshot is pending. An empty instances
with loading: false and no failure is a confirmed "none".
Rows the read discipline refused (InvalidDoc: a newer data
model, or a corrupt shape) — skipped from instances and flagged
here, so one bad row can't fail the listing while a silently short
list stays impossible. Empty when every row parsed.
A reactive instance list:
instancesis set only for a ready snapshot.