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/dev/cdev.c

@@ -149,9 +149,10 @@ memread(struct inode *ip, uint64 off, char *dst, int n)
     case 1: return consoleread(ip, off, dst, n); 
     case 2: return nullread(ip, off, dst, n);    
     case 3: return consoleread(ip, off, dst, n);
-    /* 10 = /dev/tty, 11..16 = /dev/tty1..tty6. consoleread resolves the
+    /* 10 = /dev/tty, 11..22 = /dev/tty1..tty12. consoleread resolves the
        minor to a terminal; see vt_for_minor(). */
     case 10: case 11: case 12: case 13: case 14: case 15: case 16:
+    case 17: case 18: case 19: case 20: case 21: case 22:
             return consoleread(ip, off, dst, n);
     case 5: return zeroread(ip, off, dst, n);
     case 7: return zeroread(ip, off, dst, n);   // /dev/full reads as zeros
@@ -169,6 +170,7 @@ memwrite(struct inode *ip, uint64 off, char *dst, int n)
   switch(ip->minor) {
     case 1: return consolewrite(ip, off, dst, n);
     case 10: case 11: case 12: case 13: case 14: case 15: case 16:
+    case 17: case 18: case 19: case 20: case 21: case 22:
             return consolewrite(ip, off, dst, n);
     case 7: return fullwrite(ip, off, dst, n);   // /dev/full: always ENOSPC
     case 3:                                      // /dev/keyboard: discarded