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

docs/architecture/desktop.md

@@ -75,5 +75,5 @@ through ACPI, and reach X as a mouse: pointer, click and tap.
 - **Touchpads are mice**: no two-finger scroll, no gestures, no palm rejection.
 - **No resolution change from inside X.** The mode is the console's; `schmode` changes the
   `vgpud` head only, and the loader's menu is where a real panel's mode is chosen.
-- **Runs as an ordinary user.** `startx` as `schos` works by group permission alone
-  ([users.md](users.md)); X itself is still a single seat with no logind or seatd.
+- **Runs as an ordinary user** where there is one: `startx` works by group permission alone
+  ([users.md](users.md)); the image has only root; X itself is still a single seat with no logind or seatd.