plan_shortid_autofill read exactly listed_columns.len() cells from
the materialised row source. When the row source produced a
different column count than the user's list, the extra columns were
silently dropped (wider → wrong data, insert succeeded) or read
out of range (narrower). Guard: if the materialised statement's
column_count differs from the listed-column count, skip auto-fill
and execute the verbatim statement so the engine reports the
mismatch — matching the non-auto-fill path. A friendly pre-flight
diagnostic remains sub-phase 3i.
Tests: VALUES with too many values; INSERT…SELECT with a wider and
a narrower projection — each rejected with nothing persisted.
claude@clouddev1
18d34d0d36