feat(v4): the screen and the keyboards

The stick, increment 1, task 2 (plan 2026-10-26-stick-1-screen-and-keyboard;
docs/v4.0.0/STICK.md 2, 5.3, 5.4). On the v4 path:
- the framebuffer is brought up after POST, cleared and dark: console text
  goes to serial only ("splash only, log on serial") until Zuse logs in;
  then the screen is the console (TTF, a blinking cursor, as v3's), and
  when she logs out it is cleared and dark again (console_fb_mirror(),
  console_fb_clear(); the mirror is on by default, so v3 is unchanged);
- the line editor and the node's KEY read every keyboard -- PS/2, USB, the
  virtio keyboard -- through the shared bridge (sk_input_getc()); the
  headless wait drops keyboard input as well as serial bytes;
- an EMERGENCY_CONSOLE_ENABLED build has the screen from the start.
The framebuffer setup is one helper both paths call (kernel_main.c).

Red (before): screen_dark_until_login 153051 (10835 lit), console/keys
153309, logout 153609, kbd_typeahead 153918, virtio_kbd aarch64 154245
and riscv64 154718; no_framebuffer 155546 passed before and after.
Green: 155926 (0 lit), 160156, 160409 (0 lit after logout), 160630,
virtio_kbd 161414 and 161820, no_framebuffer 161206; usb_kbd with the USB
keyboard the only one (-machine i8042=off) 164548, v3 control 164757;
the identity gate's sessions 162245-163802 all pass; v3 typed by keyboard
164009, 164115. (usb_kbd 160857 and 164313 failed in the harness:
input-send-event's device names a display, not a keyboard.)
Accepted: suite EXIT 0; three clean qemu boots, POST 538/538, dict_hash
0xfec8c47cfc6f437f unchanged (174704, 174911, 175315); test-32, 39
modules, 0 failures.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

kernel/src/kernel_main.c

@@ -465,6 +465,21 @@ void kernel_main(BootInfo *boot_info) {
 }
 
 #ifdef STARFORTH_ENABLE_VM
+/* The framebuffer the firmware handed over, as the console's screen, in
+ * the pixel format GOP reported. Both systems' boots call it. */
+static void sk_console_fb_from_boot(const BootInfo *boot_info)
+{
+    if (boot_info->framebuffer.base != NULL && boot_info->framebuffer.size > 0) {
+        FbPixelFormat fb_fmt;
+        switch (boot_info->framebuffer.pixel_format) {
+            case (UINT32)PixelRedGreenBlueReserved8BitPerColor: fb_fmt = FB_PIXEL_RGBX32; break;
+            case (UINT32)PixelBlueGreenRedReserved8BitPerColor: fb_fmt = FB_PIXEL_BGRX32; break;
+            default: fb_fmt = FB_PIXEL_BGRX32; break;
+        }
+        console_fb_init(&boot_info->framebuffer, fb_fmt);
+    }
+}
+
 /* The logger after POST: whatever --log-level asked for (default: LOG_WARN).
  * Both systems' boots call it once POST is done. */
 static void sk_log_level_after_post(const BootInfo *boot_info)
@@ -523,6 +538,15 @@ static void sk_v4_block_chain(void)
     } else {
         console_println("Artemis: virtio-blk found, and could not be attached");
     }
+
+    /* The screen and the keyboards, as the v3 path has them: the screen is
+     * cleared and stays dark -- console text goes to serial only -- until
+     * Zuse logs in (docs/v4.0.0/STICK.md 2 and 5.3; sk_v4_identity.c turns
+     * it on). The virtio keyboard is the riscv64/aarch64 machines'; a
+     * no-op where there is none. */
+    console_fb_mirror(0);
+    sk_console_fb_from_boot(sk_v4_boot_info);
+    (void)virtio_input_find_keyboard();
 }
 #endif
 
@@ -842,15 +866,7 @@ static void kernel_main_deep(BootInfo *boot_info) {
      * see 4.5f) in exchange for the fuller on-screen record; Captain Bob's
      * call, made after 4.5f's -O2 experiment showed the earlier indefinite
      * -O0 stall was a compiler-optimization problem, not a correctness one. */
-    if (boot_info->framebuffer.base != NULL && boot_info->framebuffer.size > 0) {
-        FbPixelFormat fb_fmt;
-        switch (boot_info->framebuffer.pixel_format) {
-            case (UINT32)PixelRedGreenBlueReserved8BitPerColor: fb_fmt = FB_PIXEL_RGBX32; break;
-            case (UINT32)PixelBlueGreenRedReserved8BitPerColor: fb_fmt = FB_PIXEL_BGRX32; break;
-            default: fb_fmt = FB_PIXEL_BGRX32; break;
-        }
-        console_fb_init(&boot_info->framebuffer, fb_fmt);
-    }
+    sk_console_fb_from_boot(boot_info);
 
     /* Copy capsule directory header to heap (has pointer field needing update) */
     CapsuleDirHeader *live_dir = (CapsuleDirHeader *)kmalloc(sizeof(CapsuleDirHeader));