feat(consume): parent reaches the reader -- excerpt field, body link, checker rule

K3-21 A. `okf consume` resolves a concept's `parent:` pointer -- a
`segment_id`, unique only inside one document's plan -- among the concepts
sharing its `source_file` (`consume.link_parents`, one pass, no file opened
again) and an excerpt carries `parent: { concept_id, title }`. Conditional
like `req_number`: a concept with no `parent` key moves no byte. A pointer
that lands nowhere is named `parent_unresolved: true`, never dropped.

The door writes ONE line into a heading-only body whose entry has a parent:
`Enclosing section: [<title>](/<bundle-relative path>)` (SPEC SS 5.1 lineage
through links, SS 6.1 the recommended absolute form and the kind in the
prose). Only such a body, so the segmented goldens' declared parents -- bodies
holding text -- are untouched. Appended AFTER structure derivation and
screened on its own (`_screened`, the `description` rule): read as body text
the link was derived into a second, unresolved `references` edge, measured on
the fixture. `segmentation.heading_only` is the one predicate the proposer and
the door share.

`okf check` gains its seventeenth rule, `parent_unfollowable`: a `parent`
that is not a concept_id and title, names its own excerpt, or names a concept
in neither `excerpts` nor `withheld` (together every considered concept).
Contract SS 8 point 6 added, the figure carries `parent`, and "additional
members are not read by the checker" now says the checker reads only the
members SS 8 names. The template tells the reader what `parent` is and that
SS 2.2 lets it read that one concept; `skill.CONDITIONAL_FIELDS` gains
`parent`. README and CLAUDE.md say what consume now reads.

Moved on purpose, each named: the SS 7.4 known-positive IS the contract
document, so `budget.known_positive` moves in every payload (13 238 / 12 893
/ 345 -> 14 455 / 14 083 / 372); `skills/okf-consume/` regenerated from the
segmented golden, whose plan declares s1 and s2 under s0 -- its example
payload now carries both parents; `test_bundle_identity` 16 -> 17 rules;
`test_shell_parent`'s byte test also accounts for the link line.

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

src/llm_ingestion_okf/skill.py

@@ -13,7 +13,8 @@ passes the UNFILLED template against a real payload (exit 0, 15 rules, 0
 findings), and passes a skill built for a different bundle against this one's
 payload. `contract_check.rule_bundle_identity` now compares the identity a
 skill declares with the identity its payload declares, so all three measured
-pairs are refused at exit 1 with one `bundle_mismatch` finding over 16 rules:
+pairs are refused at exit 1 with one `bundle_mismatch` finding over 16 rules
+(17 since K3-21's `parent_unfollowable`):
 a skill against another bundle's payload, the unfilled template against a real
 payload, and -- the arm an id comparison would miss -- a payload sharing the
 skill's `bundle_id` at a foreign `ref`. The right pair is untouched at exit 0
@@ -99,6 +100,7 @@ CONDITIONAL_FIELDS = (
     "verified",
     "req_number",
     "sources",
+    "parent",
 )
 
 #: Tokens too short to carry a question. The same floor the pre-pass's own
@@ -337,14 +339,16 @@ def render(
     bundle_id = okf_consume.root_bundle_id_of(bundle_root, profile=profile)
     ref = okf_consume.bundle_ref(bundle_root, profile=profile)
     concept_ids = okf_consume.enumerate_concepts(bundle_root, profile=profile)
-    concepts = [
-        okf_consume.read_concept(
-            bundle_root / f"{concept_id}{profile.paths.concept_suffix}",
-            bundle_root=bundle_root,
-            root_bundle_id=bundle_id,
-        )
-        for concept_id in concept_ids
-    ]
+    concepts = okf_consume.link_parents(
+        [
+            okf_consume.read_concept(
+                bundle_root / f"{concept_id}{profile.paths.concept_suffix}",
+                bundle_root=bundle_root,
+                root_bundle_id=bundle_id,
+            )
+            for concept_id in concept_ids
+        ]
+    )
     if not concepts:
         raise SkillError(
             f"{bundle_root} has an index but no concept under it; a skill for an "