fix(structure): the index resolves a parent naming a segment of its own document

K3-21 C. `resolve_structure` asks `_segment_lookup` first for a `parent`
edge: `(source_file, segment_id)` -> concept name, keyed off each concept's
own frontmatter (`DocumentStructure.declared`, no file read again), so a
pointer lands only inside the pointing concept's document -- `p1` exists in
every document of a multi-document bundle. A value no segment answers to is a
document number and is looked up exactly as before; a pointer naming nothing
keeps `UNRESOLVED_MARKER`. The rendering rule is untouched: a resolved
relation renders as its subject, so `parent: p1977?` becomes `parent: p1977`.

Moved on purpose, each named: both segmented goldens' index files
(`examples/ingest-golden-segmented{,-okf-v0-2}/expected-bundle/krav/1-{1,2}/
index.md`), whose declared parents s1 and s2 -> s0 rendered `parent: s0?`
while s0 stood in the bundle -- four lines, `?` removed. The four goldens
`test_the_four_existing_goldens_are_untouched` guards are not among them.
`skills/okf-consume/` regenerated, because the golden's index bytes -- and so
its ref -- moved. `test_shell_parent`'s byte test now expects the resolved
facet. README and CLAUDE.md no longer say the index renders it unresolved.

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

tests/test_shell_parent.py

@@ -179,7 +179,8 @@ def test_a_build_without_the_flag_is_the_build_with_the_opt_out(tmp_path: Path)
         text = (flagged / relative).read_text(encoding="utf-8")
         if relative.name == "index.md":
             after = text.split("\n")
-            assert [re.sub(r"parent: p\d+\?; ", "", line) for line in after] == before
+            # Resolved since K3-21 C: the concept the pointer names is here.
+            assert [re.sub(r"parent: p\d+; ", "", line) for line in after] == before
             continue
         text, links = re.subn(r"\n\nEnclosing section: \[[^\]]+\]\(/[^)\s]+\)\n\Z", "\n", text)
         linked += links