Add C backend to nxc-frontend:
- Implement CEmitter with HIR-to-C translation
- Add emit_c() function for code generation
- Support function prototypes, statements, expressions, and control flow
- Generate C11-compatible code with proper type mapping
- Add main() wrapper generation for entry points
Extend driver crate with build pipeline:
- Add emit_c_from_frontend() to generate C source from HIR
- Add write_c_file() to write generated
nessi
1e30c05233