introduce a stable NTL_DDK driver ABI to replace direct HAL_API and kernel-header access in drivers, add code/kernel/io_ddk.c and code/public/ntlite/ddk/ headers, change DriverEntry to take (const NTL_DDK*, NTL_DRIVER_INIT*), update kmain to build the DDK once via IoInitializeDdk/IoGetDdk and hand it to both boot and runtime drivers, downgrade code/public/ntlite/ddi/io_driver.h to a legacy I/O model header pulling from ntlite/ddk instead of kernel internals, move code/third_party/lwip into code/drivers/net/lwip/third_party, fix up lwip_sources.txt and build.c include paths to match, split build.c's single CFLAGS macro into COMMON/KERNEL/USER/BOOT/DRIVER cflags.

code/public/ntlite/ddk/mutex.h

@@ -0,0 +1,28 @@
+// Public nt-lite DDK mutex declarations.
+
+#pragma once
+
+#include <ntlite/status.h>
+#include <ntlite/ddk/list.h>
+#include <ntlite/ddk/object.h>
+#include <ntlite/ddk/sync.h>
+#include <ntlite/ddk/thread.h>
+
+typedef struct MUTEX {
+    OBJECT Header;
+    SPINLOCK Lock;
+    THREAD* Owner;
+    LIST_ENTRY WaitList;
+} MUTEX;
+
+// Creates a mutex object.
+__declspec(dllexport) KSTATUS KeMutexCreate(MUTEX** out);
+
+// Acquires a mutex, blocking when necessary.
+__declspec(dllexport) KSTATUS KeAcquireMutex(MUTEX* mutex);
+
+// Attempts to acquire a mutex without blocking.
+__declspec(dllexport) KSTATUS KeTryAcquireMutex(MUTEX* mutex);
+
+// Releases a mutex.
+__declspec(dllexport) void KeReleaseMutex(MUTEX* mutex);