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

K3-21 C, red. `structure` read `parent` as a document number only; a
`segment_id` answers to no key its lookup builds, so every `--shell-parent`
pointer rendered unresolved (`parent: p1977?`, 675 of 675 on one standard)
and both declared parents in each segmented golden render `parent: s0?` --
while the concept each names stands in the bundle.

Held here: a segment pointer resolves among the concepts sharing the
pointer's `source_file`; the same id in another document is not the parent; a
pointer naming nothing still carries `UNRESOLVED_MARKER`; a parent that is a
document number resolves as before; the flagged fixture build's index renders
no parent unresolved.

3 of 5 red on 46e555d; the two green are the unchanged routes.

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

tests/test_parent_index.py

@@ -0,0 +1,94 @@
+"""The index resolves a `parent` that names a segment of the same document.
+
+K3-21 C. The index is a projection of each concept's frontmatter, and
+`structure` read `parent` as a document NUMBER only: its lookup answers to a
+concept's name, its `source_file` and that file's stem, and to document
+numbers. A `segment_id` answers to none of them, so every pointer
+`--shell-parent` writes rendered unresolved (`parent: p1977?`) while the
+concept it names stands in the bundle -- 675 of 675 on one standard, and both
+declared parents in each segmented golden (`parent: s0?`).
+
+A segment id is unique only inside the plan of ONE document, so it is looked
+up among the concepts sharing the pointing concept's `source_file`, never
+across the bundle. `UNRESOLVED_MARKER` keeps its meaning: a pointer that names
+nothing still says so. The same key carries a declared segment id and a
+derived document number (`inbox.py`), and the number route is unchanged.
+
+`sts-inherit.xml` is hand-written in an invented setting and carries no
+sentence from any source.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from llm_ingestion_okf import cli, structure
+
+FIXTURE = Path(__file__).parent / "fixtures" / "sts-inherit.xml"
+
+
+def _doc(**values: str) -> structure.DocumentStructure:
+    return structure.structure_from_frontmatter(values)
+
+
+def _parent(documents: dict[str, structure.DocumentStructure], name: str) -> str:
+    resolved = structure.resolve_structure(documents)
+    return structure.facet_values(name, resolved, ("parent",))["parent"]
+
+
+def test_a_parent_naming_a_segment_of_the_same_document_resolves() -> None:
+    documents = {
+        "a/one.md": _doc(title="One", source_file="a.xml", segment_id="p1"),
+        "a/two.md": _doc(title="Two", source_file="a.xml", segment_id="p2", parent="p1"),
+    }
+    resolved = structure.resolve_structure(documents)
+    edge = next(edge for edge in resolved.edges if edge.kind == "parent")
+    assert edge.target == "a/one.md"
+    assert _parent(documents, "a/two.md") == "p1"
+
+
+def test_the_same_segment_id_in_another_document_is_not_the_parent() -> None:
+    documents = {
+        "a/one.md": _doc(title="One", source_file="a.xml", segment_id="p1"),
+        "b/one.md": _doc(title="One", source_file="b.xml", segment_id="p1"),
+        "b/two.md": _doc(title="Two", source_file="b.xml", segment_id="p2", parent="p1"),
+    }
+    resolved = structure.resolve_structure(documents)
+    edge = next(edge for edge in resolved.edges if edge.kind == "parent")
+    assert edge.target == "b/one.md"
+
+
+def test_a_pointer_naming_nothing_still_says_so() -> None:
+    documents = {
+        "a/two.md": _doc(title="Two", source_file="a.xml", segment_id="p2", parent="p9"),
+    }
+    assert _parent(documents, "a/two.md") == "p9" + structure.UNRESOLVED_MARKER
+
+
+def test_a_parent_that_is_a_document_number_resolves_as_before() -> None:
+    documents = {
+        "n1.md": _doc(title="N1", source_file="n1.md", number="1"),
+        "n11.md": _doc(title="N11", source_file="n11.md", number="1.1", parent="1"),
+    }
+    resolved = structure.resolve_structure(documents)
+    edge = next(edge for edge in resolved.edges if edge.kind == "parent")
+    assert edge.target == "n1.md"
+    assert _parent(documents, "n11.md") == "1"
+
+
+def test_the_flagged_build_s_index_renders_no_parent_unresolved(tmp_path: Path) -> None:
+    inbox = tmp_path / "inbox"
+    inbox.mkdir()
+    (inbox / FIXTURE.name).write_bytes(FIXTURE.read_bytes())
+    bundle = tmp_path / "bundle"
+    argv = ["build", str(inbox), "--bundle", str(bundle), "--bundle-id", "inherit-fixture"]
+    assert cli.main([*argv, "--okf-version", "0.2", "--shell-parent"]) == 0
+    facets = [
+        line
+        for index in bundle.rglob("index.md")
+        for line in index.read_text(encoding="utf-8").split("\n")
+        if "parent: " in line
+    ]
+    # The four shells with an ancestor holding text (`tests/test_shell_parent.py`).
+    assert len(facets) == 4
+    assert not [line for line in facets if "?" in line.split("parent: ", 1)[1].split(";")[0]]