Record networking and DMA development progress

Add the current OS source tree, build scripts, system image layout, and development notes covering DMA page allocation, e1000 bring-up, net API dispatch, and DHCP work in progress.

CODE/UTSM/kernel/log.c

@@ -0,0 +1,34 @@
+#include <utsm/log.h>
+
+static void log_line(const char *level, const char *msg) {
+    serial_write(level);
+    serial_write(" ");
+    serial_write(msg);
+    serial_write("\n");
+}
+
+void log_info(const char *msg) {
+    log_line("[INFO]", msg);
+}
+
+void log_warn(const char *msg) {
+    log_line("[WARN]", msg);
+}
+
+void log_error(const char *msg) {
+    log_line("[ERR ]", msg);
+}
+
+void log_hex64(const char *prefix, u64 value) {
+    static const char hex[] = "0123456789abcdef";
+    char buf[19];
+    buf[0] = '0';
+    buf[1] = 'x';
+    for (int i = 0; i < 16; i++) {
+        buf[2 + i] = hex[(value >> ((15 - i) * 4)) & 0xf];
+    }
+    buf[18] = 0;
+    serial_write(prefix);
+    serial_write(buf);
+    serial_write("\n");
+}