hello_off_c.nx

hello_off_c.nx -- the smallest "off C" demonstration. A standalone NishiLang program that exits with code 30. Used by the off-c stage-1 bootstrap proof to verify that nxc.elf can compile programs OTHER than its baked-in demo. Why exit 30: matches the demo's chosen sentinel so the same validation pipeline works. NOTE: deliberately has NO `import` directives. __syscall is a nxc2 intrinsic, not a runtime function. Imports trigger expand_imports's file-system walk, which under Docker requires the runtime/ tree to be visible -- skip that wrinkle for the stage-1 proof.