fix(accounting): a corpus that measures no class says so in row 6 (H6)

`measures_no_class(units)` returns a sentence when EVERY document of a
corpus has no declared fate, and row 6 prints it beside that corpus's
tally. On N200 that is 16 549 elements of `u` which look like a finding
about the build and are a finding about the run: the build exits 2 on
0 proposed plans before the accounting door is reached, so no
accounting file exists to read a fate from.

The function's docstring carries what it would take, because that is a
capability and not a threshold: `.json` is read as generic JSON, and
the publisher's STS delivery in that form would have to reach the
markdown grammar `_extract_xml` writes for the XML one. Measured
2026-09-19, with the query validated against a known positive:
`standardContent` occurs 0 times in `src/` and 4 in the witness.

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

tools/okf_accounting_gate.py

@@ -505,6 +505,11 @@ class Unit:
         )
 
 
+#: The note `_document_unit` leaves when the run declared no fate at all for a
+#: document -- because the build never reached the accounting door.
+NO_DECLARED_FATE = "no declared fates"
+
+
 def _conservation_held(build: Build) -> bool:
     return build.exit_code == 0 and "K1b FAILED" not in build.log
 
@@ -552,7 +557,7 @@ def _document_unit(
     images: list[Mapping[str, Any]] = list(entry.get("images", []))
     total = sum(elements.values())
     if declared is None:
-        return Unit(name, "document", total, 0, notes=["no declared fates"])
+        return Unit(name, "document", total, 0, notes=[NO_DECLARED_FATE])
     if not version_ok:
         return Unit(
             name,
@@ -1010,6 +1015,35 @@ def clean_in_every_run(runs: Sequence[Sequence[Unit]]) -> int:
     return sum(1 for parts in zip(*runs) if all(unit.clean for unit in parts))
 
 
+def measures_no_class(units: Sequence[Unit]) -> str | None:
+    """Did this corpus fail to measure ANY element class at all? (H6)
+
+    Reproduced on N200 Vegbygging:2024, 2026-09-19: `okf build` proposes 0
+    plans on it, prints `FAILED - no segmentation plans` and exits 2 BEFORE
+    the accounting door -- no accounting file is written. Every element then
+    lands as `u` with no declared fate, and 16 549 unaccounted reads like a
+    finding about the build when it is a finding about the run.
+
+    What it would take is a capability and not a threshold: `.json` is read as
+    generic JSON, and the publisher's STS delivery in that form would have to
+    reach the same markdown grammar `_extract_xml` writes for the XML one. No
+    such reader exists in the package -- `standardContent` occurs 0 times in
+    `src/` and 4 times in this gate's witness (measured 2026-09-19).
+    """
+    documents = [u for u in units if u.kind == "document"]
+    if not documents:
+        return None
+    blank = [u for u in documents if NO_DECLARED_FATE in u.notes]
+    if len(blank) != len(documents):
+        return None
+    return (
+        f"{len(blank)} of {len(documents)} document(s) have no declared fate: the build "
+        "did not reach the accounting door, so this corpus measures no element class. "
+        "`.json` is read as generic JSON; an STS delivery in that form would have to "
+        "reach the markdown grammar the XML reader writes."
+    )
+
+
 def refused_whole(documents: Mapping[str, Any], build: Build) -> str | None:
     """Did this run persist NOTHING of a corpus that holds documents?
 
@@ -1095,6 +1129,9 @@ def row6(r761: Path | None, n200: Path | None, ci: bool) -> Row:
                     f"    {len(doubled)} file(s) carried through the document AND rejected, "
                     f"e.g. {doubled[0].name}"
                 )
+            blank = measures_no_class(units)
+            if blank is not None:
+                details.append(f"    gate {label}: {blank}")
             if label == "default":
                 whole = refused_whole(documents, build)
                 if whole is not None:

tools/okf_gate_mutants.py

@@ -272,7 +272,7 @@ MUTANTS: tuple[Mutant, ...] = (
         "X2 a report may declare a document rejected while the bundle holds it",
         GATE,
         '    if status == "rejected" and persisted:\n        invalid += 1',
-        '    if False:\n        invalid += 1',
+        "    if False:\n        invalid += 1",
     ),
 )