Twelve login terminals, root only, console fixes, a faster build, a Niveus splash, and X back on evdev

- tty1-tty12 all run login; the image has only root. /dev/tty7..12 could not
  be written (cdev.c knew minors 10-16 only), which sent their jobs into a
  restart storm that took the supervisor down; fixed, and stat reports them as
  Linux's tty7..12.
- Erasing text at a prompt did nothing: erase_one sent a bare backspace, which
  only moves; it and the echo path now send back-blank-back through vt_feed.
- A white cursor block was left at the end of every line of a verbose boot:
  a line feed at the bottom scrolls the pixels, cursor included, and the
  cursor was erased after the scroll. It comes off first now. A blank cell is
  also marked dirty, which it was not.
- ldlsd died with a general protection fault on real hardware in its variadic
  log function: Linux module code calls with an 8-byte-aligned stack and an
  unset %al, and the prologue's movaps faults. LDLS guest code is built with
  -mstackrealign.
- make iso took over a minute for any change, because staging r8169 rewrote
  the same files and every mtime moved; it now replaces files only if their
  contents differ (about 10 s).
- The loader's splash is redrawn in the boot manager's style, and the boot
  manager shows its cursor whenever a pointer device exists.
- xf86-input-libinput is out of the image again: with it Xorg took both
  keyboard and pointer from libinput and, on the user's laptop, neither worked.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EVRhxi9zpdW2uDUN4FVcao

kernel/core/console.c

@@ -302,7 +302,7 @@ consputc(int c)
     uartputc('\b'); uartputc(' '); uartputc('\b');
     if (!cons_serial_only) {
       struct vt *v = vt_current();
-      vt_putc(v, '\b'); vt_putc(v, ' '); vt_putc(v, '\b');
+      vt_feed(v, '\b'); vt_feed(v, ' '); vt_feed(v, '\b');
     }
     return;
   }
@@ -452,8 +452,12 @@ erase_one(struct vt *v)
   v->in.e--;
   if (v->tio.c_lflag & ECHOE) {
     if (v == vt_current()) { uartputc('\b'); uartputc(' '); uartputc('\b'); }
-    if (!cons_serial_only)
-      vt_putc(v, '\b');
+    // Back, blank, back -- and through vt_feed, which keeps the text cursor
+    // in step. A bare \b only moves (see vt.c), so this used to leave the
+    // rubbed-out character on screen and the cursor block behind it.
+    if (!cons_serial_only) {
+      vt_feed(v, '\b'); vt_feed(v, ' '); vt_feed(v, '\b');
+    }
   }
 }