Debug-info reader: turns .debug_info (DWARF) into typed function
signatures the decompiler can attach to its FnDecl AST nodes.
v0 scope: x86-64 ELF, DWARF 4/5. Subprogram DIEs yield names,
addresses, and parameter / return types. Type recovery covers
DW_TAG_base_type (primitives) and DW_TAG_pointer_type (recursively
resolved); other tags produce [ud_ast::Type::Unknown].
Pluggable parsers for PDB, stabs, and Mach-O .dSYM will land in
this same crate as additional modules.