kernel: kernel_boot reads microcode from each initramfs image (issue 1977, L6)

Replaces the state record read (root's 0700) with images_with_microcode per /boot/initramfs-*.img:
true when the first 64 KiB hold a path under kernel/x86/microcode/; an unreadable image goes to
image_errors with its error. Test: 1977/AC5.

Builds: L6 (issue 1977 note 3)

modules/kernel/cmd/kernel-tools/main.go

@@ -52,7 +52,7 @@ func tools(m *Machine) []stdio.Tool {
 				"(systemd-boot, read from the EFI variable it sets, grub, or none), the menu's entries, the kernels in /boot, the entry " +
 				"the machine booted (systemd-boot) or the kernel image it booted (grub), whether the fallback kernel linux-lts is on " +
 				"the menu with its kernel in /boot, and the room free on /boot in KiB (the fallback kernel needs about 72 MB), the microcode revision the CPU runs " +
-				"(/proc/cpuinfo) and whether the initramfs images were built with the microcode drop-in (novox/hq issue 1977). " +
+				"(/proc/cpuinfo) and, per /boot/initramfs-*.img, whether its early cpio carries microcode (images_with_microcode; an unreadable image is named in image_errors) (novox/hq issue 1977). " +
 				"Replaces ls /boot, bootctl list, reading grub.cfg and df /boot. (r)",
 			Input: schema(map[string]any{}),
 			Run:   func(args map[string]any) (any, error) { return m.Boot() },