test(b-gate): the pin moves 8 -> 15, and names the two steps that still share a door

`_EXTERNAL_TODAY` and `_WITH_A_DOOR_TODAY` are the arm's own count, not the gate's, so
the seven new doors have to be written down here before the suite agrees they exist. The
two assertions that pinned `kjørekonfig`/`utboks`/`prepass-artefakt`/`parse-feil` as
door-LESS are inverted rather than deleted: they were the arm's discriminator, and a
door that silently went away must still turn this red.

The manifest count moves 514 -> 515 for the one new probe file.

Also a probe for the shape guard: the writers take `Mapping`/`Sequence` and would
serialize whatever they were handed, so a list where an object belongs would become a
valid file with the wrong shape and the run that reads it later would be the one to
fail. The door refuses it as a 3 (the call parsed, so 2 is the wrong code) and leaves no
directory behind. Carries its rc-0 control.

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

tests/test_toolbox_outbox_doors.py

@@ -391,3 +391,34 @@ def test_write_debate_tools_from_outside_writes_an_empty_trace_as_a_statement(
     assert len(paa_disk["tool_calls"]) == len(kall)
     assert len(paa_disk["requirements"]) == len(krav)
     assert paa_disk["tool_calls"][1]["arguments"]["query"] == "varme"
+
+
+# --- formvakten -------------------------------------------------------------------------------
+
+
+def test_a_payload_of_the_wrong_shape_is_refused_rather_than_written(tmp_path: Path) -> None:
+    """Skriverne tar `Mapping`/`Sequence` og ville serialisert hva som helst de fikk: en liste der
+    et objekt hører hjemme blir en gyldig fil med feil form, og kjøringen som leser den SENERE er
+    den som feiler. Døren feller formen med en gang, og gjør det som en avvisning (3) — kallet
+    parset, så 2 ville vært feil kode."""
+    ut = tmp_path / "ut"
+    feil = _json_arg(tmp_path / "feil.json", ["ikke", "et", "objekt"])
+    proc = _toolbox(
+        "write-proposal-reviews", "--outbox-dir", str(ut), "--run-id", _RUN, "--payload", feil
+    )
+    assert proc.returncode == 3, proc.stdout
+    assert json.loads(proc.stdout)["error"]["kind"] == "ValueError"
+    assert not ut.exists(), "en avvist form skal ikke ha lagt igjen en katalog eller en fil"
+    # rc-0-kontroll: SAMME dør, samme sti, riktig form. Uten den ville armen vært grønn mot en
+    # dør som avviste alt.
+    ok = _toolbox(
+        "write-proposal-reviews",
+        "--outbox-dir",
+        str(ut),
+        "--run-id",
+        _RUN,
+        "--payload",
+        _json_arg(tmp_path / "rett.json", {"reviews": []}),
+    )
+    assert ok.returncode == 0, ok.stderr
+    assert Path(json.loads(ok.stdout)["path"]).is_file()