refactor!: switch variadic spread to postfix syntax

[ivov]

Warning

This is a breaking change!

Switches variadic spread from prefix f(..xs) to postfix f(xs...)

I failed to anticipate parser ambiguity between range and spread: f(..xs) (spread) and f(..5) (range) are identical in the token stream, so the parser reads in spread when it first finds ... This was blocking two of the five range shapes (..N and ..=N) from appearing as inline call arguments to any range-accepting function.

Postfix spread now aligns with Go's callsite syntax and frees .. to be a range operator everywhere.

// before
fmt.Println(..parts)

// after
fmt.Println(parts...)

[github-actions]

Released in lisette-v0.2.0