Implement GDT and basic IDT setup

This commit adds GDT initialization with proper code/data segments and reloads CS.

It also adds the initial IDT structure and loads an empty IDT.

Build configuration updated to disable SSE/MMX to prevent compiler generation of unsupported instructions in early boot.

test_images.sh

@@ -12,11 +12,6 @@ if [ ! -f "$RELEASE_DIR/claude-os.iso" ]; then
     exit 1
 fi
 
-if [ ! -f "$RELEASE_DIR/claude-os.img" ]; then
-    echo "Error: claude-os.img not found!"
-    exit 1
-fi
-
 echo "Testing ISO image..."
 timeout 5s qemu-system-i386 -cdrom "$RELEASE_DIR/claude-os.iso" -debugcon file:iso_output.txt -display none -no-reboot || true
 if grep -q "Hello, world" iso_output.txt; then