Key-value and where-pair plans had no row limit, so a selector pointed at a history
or events table materialised every matching row on every poll. ISqlDialect gains
RowLimitPrefix/RowLimitSuffix(n) (SQL Server TOP (n), Postgres LIMIT n, Oracle FETCH
FIRST n ROWS ONLY); plans carry a RowCap (distinct keys, or 1) and ask for RowCap+1
rows; the reader also stops client-side at RowCap+1. Getting the extra row proves the
selector ambiguous: the group publishes BadConfigurationError with a rate-limited
warning. The reader reports those answered refusals so the driver counts them as
answer evidence, and any refusal-only poll now restores Healthy after a comms fault.
Refs #744
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Joseph Doherty
0a5aa9fc43