Replace `_impl` aliases in `R/bipartite.R`

[krlmlr]

Goal
Review the code in R/bipartite.R and replace all direct _impl function aliases with explicit wrapper functions.

Functions to update:

• bipartite_projection_size <- bipartite_projection_size_impl
• bipartite_mapping <- is_bipartite_impl

Instructions

1. Review the code to understand the function signatures
2. Create explicit wrapper functions that forward to the _impl functions
3. Forward each argument individually and explicitly using arg = arg notation
4. Do not use ... unless the _impl function itself uses ...

Pattern
Replace direct aliasing like:

func_name <- func_name_impl

With an explicit wrapper:

func_name <- function(arg1, arg2, ...) {
  func_name_impl(
    arg1 = arg1,
    arg2 = arg2,
    ...
  )
}

File
R/bipartite.R