docs: delta wire form and status cadence; require four status frames

harness/mame/vidstream.lua

@@ -977,7 +977,7 @@ local function dump_stream(timed_out)
 		#captures, #table.concat(chunks), DUMP_DIR))
 
 	local ok = okb and okt and not timed_out and bad_captures == 0
-		and #captures >= 3 and last ~= nil
+		and #captures >= 4 and last ~= nil
 		and last.frames_rx == STREAM_FRAMES and last.drops == 0
 		and last.crc_err == 0
 	print(ok and "VID: RESULT PASS" or "VID: RESULT FAIL")