docs(limitations): withdraw the "two variables" explanation -- 394 was a scoping artifact

Yesterday's-shape correction, one commit old. e25de56 explained the 2400-vs-2401
gap by saying the corpus "grew from 389 files to 394 between the two runs", so
the larger snapshot returned one fewer URL -- two variables moving at once.

The consumer self-corrected the same day and the correction reproduces here
against their tree, not against their message:

  find skills -path '*/references/*' -name '*.md'   389
  find skills -name 'SKILL.md'                        5
  find skills -name '*.md'                          394

394 is every .md under skills/; 389 is the references/** path the measurement
actually scoped to. One snapshot counted two ways, not two snapshots taken at
different times -- and the 5 SKILL.md files contributed no unique URLs.

So the corpus never grew, only the script moved, and the one-URL gap is back to
unexplained (the original harvester is gone from a scratchpad). Everything else
in their measurement stands unchanged: 2400 distinct URLs, 0 firings on the
entropy branch, worst legitimate token H=4.301 at len=78.

The do-not-merge rule is unaffected and now rests on less: two counts of the
same knowledge base, one URL apart, no account of why. Never summed, never
quoted as one figure.

27 items unchanged, README stays in sync.

docs/LIMITATIONS.md

@@ -178,10 +178,15 @@ items; this is the full list, each with the mechanism.
   (`is_ordinary_url` is False on the `%` rule) and still not a reason to move the
   threshold — but the margin this bullet reports is much thinner than 4.04 implies.
   Note the corpus count: 2400 is a rebuilt harvester's, where the 2401 in the next
-  bullet is the earlier run's. The difference is not only the script — the corpus also
-  grew from 389 files to 394 between the two runs, so the *larger* snapshot returned one
-  *fewer* distinct URL. Two variables moved at once, which means neither count explains
-  the other: they are not interchangeable, and must not be summed or quoted as one figure.
+  bullet is the earlier run's. Same knowledge base, one URL apart. An earlier version of
+  this note offered a second moving variable — a corpus that "grew from 389 files to 394"
+  — and that explanation is **withdrawn**: the consumer corrected it the same day, and the
+  counts reproduce here against their tree. 394 is every `.md` under `skills/`; 389 is the
+  `references/**` path the measurement actually scoped to; the 5 `SKILL.md` files between
+  them contributed no unique URLs. That is one snapshot counted two ways, not two
+  snapshots. So only the script moved, and the one-URL gap stays *unexplained* — the
+  original is gone from a scratchpad and nobody has chased it. The counts remain
+  non-interchangeable: never summed, never quoted as one figure.
 - **Legitimate CDN content-asset ids trip the hex branch, permanently.** A ≥32-char
   hex path segment is opaque by design, and several public CMSes mint asset URLs that
   way (measured: 9 distinct on `regjeringen.no`, `ks.no`, `datatilsynet.no`). This is