Split a rest/repeating parameter's name into its base and starting number: the trailing digits (or
1 if none), so number → { base: 'number', n: 1 } and values2 → { base: 'values', n: 2 }.
Parameters
raw: string
Returns {base:string;n:number}
Remarks
The shared numbering convention — the signature (toSlots in FunctionPreviewPanel) and the
argument form (toArgRows) MUST agree on it, or SUM's second slot reads number2 in the
hint and number1 in the form.
Split a rest/repeating parameter's name into its base and starting number: the trailing digits (or
1if none), sonumber→{ base: 'number', n: 1 }andvalues2→{ base: 'values', n: 2 }.