Excel renders numeric cells with the General format in the shortest
form, so database values like 0.3500000 exported from decimal columns
displayed as 0.35 and the declared scale looked truncated (#8225).
Pre-register one 0.0...0 number format per fractional-digit count (up
to 15) plus right/left alignment variants after the six fixed styles,
and switch fractional numeric cells to the matching format so Excel
keeps the decimals visible. Exponent-notation values and scales beyond
15 decimals keep the previous General rendering.
Refs: #8225