harness: identify the level-1 video-memory test that raises code 0x100 (VIDEO MEMORY-22)

The dispatch status is 0x100 (printed as '22' in the message). A driver-side
transparent low-RAM write log (VT1200_LOWLOG) shows the slot at bit 0x16F0 is
written by the store at 3FDF9090 from a13(0x10), which L3FA7C050 sets to the
literal 0x100 when the memory test L3F2018B0 returns non-zero. L3F2018B0 is the
level-1 video-memory test (base bit 0x04000000, count 0x20000). Its failing
checks: the 16-bit walking-bit read-back at 0x04000000 (baseline, unmapped) and,
with video RAM mapped, the REFCNT (0xC00001F0) 'must change' check.

harness/mame/code22_final.lua

@@ -0,0 +1,37 @@
+-- code22_final.lua -- clean evidence capture for CODE22_REPORT.md
+--
+-- Prints, in order: the memory test's loaded args, the walking-bit read vs
+-- expected, the walking-bit failure exit, the DRAM refresh-counter compare,
+-- the memory test's return value, and L3FA7C050's final return.
+--
+--   CFF_FRAMES=300 <mame> vt1200 ... -autoboot_script harness/mame/code22_final.lua
+
+local machine = manager.machine
+local cpu = machine.devices[':maincpu']
+local dbg = machine.debugger
+if not dbg then print("ERROR: no debugger"); machine:exit(); return end
+
+local function bp(addr, fmt, regs)
+	dbg:command(string.format('bpset %s,,{ printf "%s\\n", %s ; g }', addr, fmt, regs))
+end
+
+bp("3f201990", "ARGS a13=%08X a7=%08X a3=%08X a4=%08X", "a13, a7, a3, a4")
+bp("3f201c20", "WALK-CMP read=%08X expected=%08X", "a11, a8")
+bp("3f201c80", "WALK-FAIL a12=%08X a8=%08X a11=%08X", "a12, a8, a11")
+bp("3f201ed0", "REFCNT-CMP a0=%08X a6=%08X", "a0, a6")
+bp("3fa7dda0", "MEMTEST-RET a8=%08X", "a8")
+bp("3fa7de30", "C050-RET-0x100 a8=%08X", "a8")
+print("breakpoints armed")
+
+local maxframes = tonumber(os.getenv("CFF_FRAMES") or "300")
+local n = 0
+emu.register_frame_done(function()
+	n = n + 1
+	if n >= maxframes then
+		print("done (" .. n .. " frames)")
+		machine:exit()
+	end
+end, "vt1200-cff")
+
+dbg.visible_cpu = cpu
+dbg.execution_state = 'run'