docs(consume,build): both parent defaults stay off, and the reason is now a measurement

K3-21 B. `cli.DEFAULT_SHELL_PARENT`'s comment said it was off because `okf
consume` reads no `parent` key; after A that sentence was false and the
default was unmeasured in both directions. Re-measured on the one standard
with heading-only sections: hit@1, hit@8 and hit@50 stay 6/6 at both k with
the known-positive at rank 1, but the link's bundle-absolute path repeats
the document's directory in 675 bodies, and the delivered set moved on 2 of
8 questions at the default k and 3 of 8 at k 50, newly delivered shells
matching the question only through that path on 1 of 3, 4 of 7 and 6 of 23
-- the saturation K3-20 took out of the id signal, back through the body.
Off.

`consume.DEFAULT_FOLLOW_PARENT`: the same delivered set as the pointer (16
of 16 payloads), 6 of 6 correct either way on questions whose answers are
never shells, at +2 488 / +2 746 B on the 2 of 8 default-k payloads holding a
linked shell and up to +20 817 B at k 50. Off.

A test holds both defaults and that the false sentence is gone.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/llm_ingestion_okf/cli.py

@@ -173,11 +173,20 @@ DEFAULT_FIRST_SPAN_FROM_ZERO = True
 #: concept count is unchanged and the cost to a consumer is a re-run.
 DEFAULT_CLOSE_SPAN_GAPS = True
 #: Round 20 (K3-20). A section whose body is its heading alone gets `parent:`
-#: naming the nearest ancestor that holds text (`propose._link_shells`). NOT a
+#: naming the nearest ancestor that holds text (`propose._link_shells`) and,
+#: since K3-21, one `Enclosing section:` link line in its body. NOT a
 #: segmentation rule: it adds no boundary and copies no text, and the concept
-#: count is unchanged. OFF, and the default is a measurement of what it buys:
-#: `okf consume` reads no `parent` key, so no payload ranks differently with
-#: it, while it moves the bytes of every bundle holding a heading-only section.
+#: count is unchanged. OFF, re-measured in K3-21 once `okf consume` read the
+#: key -- the reason it was off before. On the one standard with shells hit@1,
+#: hit@8 and hit@50 stay 6/6 at both k with the known-positive at rank 1, but
+#: the link's bundle-absolute path repeats the document's directory in 675
+#: bodies, and the delivered set moved on 2 of 8 questions at the default k
+#: and 3 of 8 at k 50, newly delivered shells matching the question ONLY
+#: through that path on 1 of 3, 4 of 7 and 6 of 23. That is the saturation
+#: K3-20 took out of the id signal, re-entering through the body. It moves the
+#: bytes of a bundle holding a heading-only section and of nothing else: 0 of
+#: 453 K2 bodies are heading-only, and the five-document folder builds
+#: byte-identical with it.
 DEFAULT_SHELL_PARENT = False
 #: Round 9. Clause 1 asked whether a title ENDED in a number, which is a
 #: question about the number rather than about the title: a drawing's dimension