port: the rate's independent leg survived a challenge, and a failure mode recurred

The Decoder re-ran both flagged findings rather than arguing them. The pulse
ratio -- the leg under rate=0.5 that is independent of the other two -- came back
0.1000 over 16 clean cycles and 0.0993 on a second capture, unchanged by the
full-quad reader. Recorded in the authored why, because a leg that has survived a
challenge to its own instrument is worth more than one merely repeated.

Unit 10's conclusion survives (the parent multiplies in, so F6's gate is
unaffected) but its quoted numbers were a printed subset standing in for the
population -- the second time that exact error has appeared in evidence this port
consumed. Recorded as a pattern rather than a slip: a summary drawn from a subset
does not look like an error, it looks like a result, and neither instance was
reachable by reasoning because the argument was valid and the inputs were wrong.

No code change: both conclusions stand.

docs/port/f6-what-starts-the-sweep.md

@@ -499,3 +499,24 @@ rotated parallelograms — **the general fact was written down before the reader
 contradicted it.** Their cheap check is worth repeating here because it applies to
 anything the port ever reads: *read one raw record in full before trusting any
 count derived from it.* The batch size was printed on every one of those lines.
+
+## 📌 And the same error recurred, which makes it a pattern rather than a slip
+
+The withdrawn alpha bound on this page failed because nine values quoted as a
+series were `sorted(set(...))[:9]` — the lowest distinct values, a tail wearing
+the shape of a trajectory. The Decoder has since found the same thing in a second
+finding: an implied-parent range quoted as 254.0–256.9 turned out to be *the rows
+they had printed*, every twentieth frame, standing in for a population whose real
+first-cycle spread was 250.9–260.5.
+
+**Twice, and both times the output looked fine.** That is the tell: a summary
+drawn from a subset does not look like an error, it looks like a result. The
+conclusion survived on both occasions, so nothing here needs undoing — but a
+conclusion surviving is not evidence the number under it was sound, and this port
+has now inherited two numbers that were not.
+
+⚠️ **Neither was reachable by reasoning**, which is the part worth keeping. In
+both cases the argument was valid and the *inputs to the summary* were wrong. No
+amount of re-reading the claim finds that; only re-running it does. It is the
+argument for re-running over re-checking, and it is why the two findings flagged
+as unverified above were re-run rather than defended.