Rounding mode should be towards zero.

[oscbyspro]

In response to changes upstream, fraction digits that exceed the maximum fraction digits length may round away from zero. This rarely matters, but sometimes the behavior may be unexpected. Assume

• diffable text field is idle
• value == 999.999
• bounds == max
• integer precision == 3
• fraction precision == 2

so that when the user interacts with the view (editing changed counts as a change upstream) the following happens

• bounds clamping rule applies: value == 999.999
• the style formats the value (and implicitly rounds it up): number == "1,000"
• precision rule applies: number is trimmed to "000" then converted: value == 0.

[oscbyspro]

The proposed solution rounds towards zero in NumericTextStyle/interpret(_:): 764c2f2. Before it can be patched, however, it should be considered if the rounding rule should be applied universally, as in:

@inlinable var format: Format {
    adapter.format.rounding(.towardZero)
}

and thereby apply to NumericTextStyle/format(_:) and NumericTextStyle/merge(_:) as well. I have a vague suspicion that it does not make any difference in NumericTextStyle/merge(_:) and that there may be an edge case in which it is reasonable in NumericTextStyle/format(_:).

[oscbyspro]

The rounding rule has been moved to all methods in: 8e96fe2.