feat(consume): the door's link line is out of the default reading

`link_in_signal` defaults to `False` on all three entry points --
`searchable_text`, `concept_scores` and `build_payload` -- through one named
constant, `DEFAULT_LINK_IN_SIGNAL`. This carries out K3-23's recommendation
(alternative c), and its numbers are the whole warrant: of the newcomers the
door's `Enclosing section:` line ever added a question token to, 39 of 39
gained it from the bundle-absolute PATH and 0 of 39 from the link's title, and
every token the path contributed is a segment of the document's own directory
-- the saturation `shared_id_prefix` takes out of the id signal, back in
through the body.

A CONSTANT rather than three naked literals, chosen against the module: the
other eight defaults here are constants (`DEFAULT_PROFILE`, `DEFAULT_LIMIT`,
`DEFAULT_TIE_SHARED_RANK`, `DEFAULT_STEM_PREFIX`, `DEFAULT_TITLE_COVERED`,
`DEFAULT_SOURCE_QUOTA`, `DEFAULT_FOLLOW_PARENT`, `DEFAULT_K`) and this was the
one default spelled out three times. It also lets a test fall on the rule from
the module that owns it.

NO CLI flag is added and none is changed. `grep -n '"--.*link'` over `src/`
gives 0 hits before and after, and `consume.main` never passed the parameter,
so the CLI inherits the function default. A flag was considered and NOT added,
because no caller could be named that needs the older reading: the three call
sites outside `consume.py` (`skill.py:360`, `tools/okf_consume_measure.py:155`
and `:247`) all inherit it deliberately.

Measured before landing: 0 of 5 shipped bundles carry the door's line
(denominators 446, 1 133, 270, 2 756, 2 761 concept files) and 5 of 5 payloads
are byte-identical across the move. The consumer repository was read only and
its tree is unchanged, listing identical including mtimes.

The docstrings move with the code rather than after it. `concept_scores` said
this was "an INSTRUMENT, not a flag and not a default" and `build_payload` that
it "carries no CLI flag"; the first is now false and the second still true, and
each says so. `cli.DEFAULT_SHELL_PARENT` keeps its value and loses its reason:
the cost it cited -- delivered sets moving through that path -- is what this
commit removes, so the comment now states why it stays off NOW, which is N = 1
document and a consumption half nobody has judged. README and CLAUDE.md carry
the same sentence where they already describe the line, measured rather than
written on reflex: neither said anything about the ranking before.

One test changed with the code. The characterisation of what the LINE does
called `concept_scores` with no parameter, because the reading it characterises
used to be the default; it now names that reading. Same fixture, same number.

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

CHANGELOG.md

@@ -28,9 +28,30 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   form -- so a human line opening with the same two words, and the door's exact
   form anywhere but last, both keep every character they have.
   `--shell-parent` therefore stays OFF at the current link form, and reading
-  the body without the line is recommended as `consume`'s default in a later
-  round: it is byte-identical on **5 of 5** bundles anyone ships today, none of
-  which carries the line.
+  the body without the line was recommended as `consume`'s default -- carried
+  out in the same unreleased block below: it is byte-identical on **5 of 5**
+  bundles anyone ships today, none of which carries the line.
+
+### Changed
+
+- **`consume` no longer scores the door's `Enclosing section:` line (K3-25).**
+  `link_in_signal` defaults to `False` (`consume.DEFAULT_LINK_IN_SIGNAL`) on
+  all three entry points -- `searchable_text`, `concept_scores` and
+  `build_payload` -- so the ranking and the stem vocabulary read a heading-only
+  body without the line the door appends under `--shell-parent`. The excerpt
+  still carries it and no CLI flag changed, so what moves is ORDER and never an
+  excerpt's bytes. Carrying out K3-23's recommendation with its numbers: of the
+  newcomers that line ever added a question token to, **39 of 39** gained it
+  from the bundle-absolute PATH and **0 of 39** from the link's title, every
+  such token being a segment of the document's own directory; under this
+  reading a flagged bundle delivers what the unflagged build delivers on **16
+  of 16** rows (list, order and `spent`), with hit@1/8/50 **6/6** at both `k`
+  and the known-positive at rank **1**. The cost to anyone shipping a bundle
+  today is zero bytes: **0 of 5** bundles carry the line, so **5 of 5** payloads
+  are byte-identical across the move. A bundle that does carry it -- only
+  `okf build --shell-parent` writes it, and that default is unchanged and still
+  OFF -- gets a different delivered order; `link_in_signal=True` is still
+  reachable for the older reading.
 
 ### Fixed