Bridge warden-ui's debug channel out of the qemu VM

The rig could drive the UI and detect one outcome: the process died. Nothing
could ask the UI what page it was on or what a tap would land on, because
that channel is a FIFO inside the guest and the initramfs is busybox-only
with no sshd. Scenarios therefore asserted nothing and screenshots went
unread.

run.sh --ctl exposes a second pci-serial port as a unix socket, the same
device the RS485 bridge already rides, listed first so it is always ttyS0.
It also puts warden.ctl on the kernel command line, and init bridges only
when that marker is present: a VM launched with --rs485 alone has a ttyS0
too, and that one is the Modbus wire. The bridge relays one command line in
and the FIFO's reply out, then a sentinel so the reader needs no timeout.

qmp.py gains the channel verbs (nav, page, stats, hit, assert_page,
assert_hit), records every step to results.jsonl as ok/fail/fatal, continues
past an assertion mismatch so one run reports every broken expectation, and
checks the console after EVERY step for the stage-2 init's EXITED line so a
crash is pinned to the step that caused it. assert_hit matches the widget's
bounding box: an icon has no usable caption and two list rows share a class,
but the geometry the UI itself resolved is exact.

The vocabulary is what tools/warden-ctl already speaks over SSH to a real
panel, so a script that runs here runs there. Verified end to end on the rig
(11/11 verbs round-tripped) and against the bench panel, where the same
commands returned byte-identical results.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013aHKWzT5EF86RFKRMtAv9n

qemu/run.sh

@@ -14,6 +14,9 @@
 #                      "device boots believing 2021" incident class
 #   --rs485 SOCK       unix socket chardev for the RS485/Modbus bridge
 #                      (pci-serial: needs the virt.fragment kernel)
+#   --ctl SOCK         unix socket to warden-ui's debug channel (nav/page/hit),
+#                      bridged by init from a pci-serial port; the rig-side
+#                      twin of tools/warden-ctl over SSH on a real panel
 #   --watchdog         add i6300esb watchdog, reset on expiry (fragment kernel)
 #   --qmp SOCK         QMP unix socket (screendump, input-send-event, quit)
 #   --display MODE     off (default, -nographic) | on (gtk window) | headless
@@ -32,7 +35,7 @@ QEMU_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 OUT="${OUT:-$QEMU_DIR/out}"
 
 KERNEL="" INITRD="$OUT/initramfs.cpio.gz" DISK="" NO_DISK=0 SLOT="_a"
-RTC="" RS485="" WATCHDOG=0 QMP="" DISPLAY_MODE="off" SHELL_FLAG=0 ALLOW_APPLY=0
+RTC="" RS485="" CTL="" WATCHDOG=0 QMP="" DISPLAY_MODE="off" SHELL_FLAG=0 ALLOW_APPLY=0
 SSH_PORT=2222 HTTP_PORT=8080 API_PORT=28443
 EXTRA=()
 
@@ -45,6 +48,7 @@ while [ $# -gt 0 ]; do
     --slot)      SLOT="${2:?}"; shift 2 ;;
     --rtc)       RTC="${2:?}"; shift 2 ;;
     --rs485)     RS485="${2:?}"; shift 2 ;;
+    --ctl)       CTL="${2:?}"; shift 2 ;;
     --watchdog)  WATCHDOG=1; shift ;;
     --qmp)       QMP="${2:?}"; shift 2 ;;
     --display)   DISPLAY_MODE="${2:?}"; shift 2 ;;
@@ -102,9 +106,21 @@ if [ -n "$DISK" ] && [ "$NO_DISK" -eq 0 ]; then
           -device "virtio-blk-device,drive=vd0" )
 fi
 [ "$SHELL_FLAG" -eq 1 ] && APPEND="$APPEND warden.shell"
+# Tells init the FIRST 8250 is the control bridge. Without this marker init
+# bridges nothing, so a VM launched with --rs485 alone never has its Modbus
+# wire mistaken for the debug channel.
+[ -n "$CTL" ] && APPEND="$APPEND warden.ctl"
 [ "$ALLOW_APPLY" -eq 1 ] && APPEND="$APPEND warden.fwapply"
 [ -n "$RTC" ] && ARGS+=( -rtc "base=$RTC" )
 [ "$WATCHDOG" -eq 1 ] && ARGS+=( -device i6300esb -action watchdog=reset )
+# The UI's debug channel, bridged out of the VM: rootfs/sbin/init relays lines
+# between this port and warden-ui's control FIFO (see qmp.py --ctl). Same
+# pci-serial the RS485 bridge rides. Listed BEFORE rs485 so that, whichever
+# combination is requested, this port enumerates as ttyS0 -- the first port
+# init's bridge probes. Put rs485 first and the bridge would be talking to the
+# Modbus wire.
+[ -n "$CTL" ] && ARGS+=( -chardev "socket,id=ctl,path=$CTL,server=on,wait=off"
+                         -device "pci-serial,chardev=ctl" )
 [ -n "$RS485" ] && ARGS+=( -chardev "socket,id=rs485,path=$RS485,server=on,wait=off"
                            -device "pci-serial,chardev=rs485" )
 [ -n "$QMP" ] && ARGS+=( -qmp "unix:$QMP,server=on,wait=off" )