Say which check failed, and read a byte from either end

Their diagnosis came back and the radio end is faultless.  Every burst is
textbook: four sync pulses at 612 microseconds, then 216 and 403 microsecond
data pulses with gaps that complete each bit period, six of them a second,
sliced cleanly at the right lengths.  The pulses this had been failing to read
were being recovered perfectly all along and the fault is in the arithmetic
after them.

Two things follow from that, and neither is a guess about their sensors.

The first is that "nothing framed" is not a diagnosis, it is the absence of
one, and it was all this could say.  A message whose checksum holds and whose
parity fails is a different fault from one where neither holds, and both
differ again from a burst that never lined up on a byte boundary -- three
faults, three fixes, one message.  So the diagnosis now reports the closest
framing it found, which of its checks held, and the bytes themselves in
hexadecimal, which is what any question about a format is actually about and
saves asking somebody to read numbers off a screen.

The second is that this still assumed something it had no business assuming:
which end of a byte goes down the air first.  Both orders are tried now and
the checksums say which, like everything else here.  That one has a
fingerprint worth knowing and worth having said in the manual: reversing the
bits of a byte does not change how many of them are set, so odd parity
survives it and a checksum does not -- a message read from the wrong end shows
every parity holding and every sum failing, on every copy, which is a
signature rather than a coincidence.

Also fixed, and found by building their burst from the timings they sent: a
real transmitter closes the last bit with a terminating pulse, so a message of
fifty-six bits arrives as sixty-one pulses rather than sixty.  Nothing here
had ever seen one, the simulator not sending it, and every test in this file
was therefore one pulse short of what comes off the air.  It happens to be
handled correctly, which is luck rather than design, so it is now what the
tests are written against.

Full suite 2339 passed.  Sixty seconds of receiver noise still yields nothing,
and four hundred seconds of the invented garden still yields no sensor that is
not there, both rechecked after adding the second byte order.  Built as
2026-09-07_04.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg

packaging/make-man.py

@@ -1411,9 +1411,13 @@ assumes as little as it can about how a bit is drawn. Not which of the pulse
 and the gap carries the bit; not whether the gap is the complement of the
 pulse or a fixed spacer, since a 220 microsecond pulse against a 200
 microsecond spacer is the longer of the two and reads as the wrong bit; and
-not which of long and short means one. The same burst is read half a dozen
-ways and the checksums say which reading it was, at most one of them being
-able to satisfy one. A transmitter running ten per cent fast is therefore read
+not which of long and short means one; and not which end of a byte goes down
+the air first. The same burst is read half a dozen ways and the checksums say
+which reading it was, at most one of them being able to satisfy one. There is
+a fingerprint for the last of those: reversing the bits of a byte does not
+change how many are set, so parity survives it and a sum does not, and a
+message read from the wrong end shows every parity holding and every checksum
+failing. A transmitter running ten per cent fast is therefore read
 correctly and never noticed, which matters: these are unlocked and drift with
 the temperature, and an outdoor sensor in January is not the one that was on
 the fence in July.
@@ -1478,8 +1482,12 @@ or three lengths with nothing in between; a smear means noise is being sliced
 as signal, or two sensors are transmitting over each other.
 .TP
 .B "clean pulse lengths, nothing framed"
-The radio is fine and the message is from a model this does not read. The line
-of pulse lengths is what is needed to add it.
+The radio is fine and the message is from a model this does not read. Under it
+comes the closest thing to a message that was found, which of its checks held,
+and the bytes themselves in hexadecimal. Which check fails says what kind of
+fault it is: a sum that holds while a parity does not is a different thing
+from neither holding. That line and the pulse lengths above it are between
+them everything needed to add a format.
 .TP
 .B "framed, but needs the same message twice"
 It was read correctly and arrived once. The two older models are believed only