Split Number Scientific into Number NumberValue

[webdevred]

JBeam (like JSON) has no semantic distinction between 1 and 1.0, BeamNG reads both identically. However, authors do write them differently, and the old formatter collapsed everything into Scientific, silently rewriting 1 as 1.0 on every format pass. This was unexpected.

This PR introduces NumberValue to track the distinction through the AST:

data NumberValue
  = IntValue Integer
  | DecimalValue Scientific

Number Scientific becomes Number NumberValue. The formatter renders IntValue with show (producing 1) and DecimalValue with formatScientific (producing 1.0), so the output matches what the author wrote.

Parser

intDecimalParser uses notFollowedBy on ./e/E after L.decimal, so 1.5 fails the integer branch and falls through to L.scientific. Both branches share the same numberParser combinator that handles the leading -.

Representation

NumberValue follows the same pattern as InternalComment, a dedicated type nested inside a single Node constructor, keeping Node's pattern match surface flat while allowing finer-grained matching where needed. numberValueToScientific in Core/Node.hs provides the canonical conversion for code that only needs a number.