moving kernel code to kernel/

src/root.zig

@@ -1,5 +1,5 @@
 //! Shared definitions that form the contract between a bootloader
-//! (src/boot/, e.g. efi.zig built as BOOTX64.efi) and the kernel (src/main.zig).
+//! (src/boot/, e.g. efi.zig built as BOOTX64.efi) and the kernel (src/kernel/main.zig).
 //!
 //! Both binaries import this as the "danos" module, so the handoff layout is
 //! defined in exactly one place.