Human-friendly demangling of Lean compiler symbol names, extending Name.demangle with prefix handling, compiler suffix folding, and backtrace line parsing. Called from the C runtime via @[export] for backtrace display.

def Lean.Name.Demangle.demangleSymbol (symbol : String) : Option String

def Lean.Name.Demangle.demangleBtLine (line : String) : Option String