bench: matrix v4 adds pid_roundtrip; correctness suite grows to 29 with three P&ID checks

tasks_v4.py extends v3 with one task the reader can fail on its own: the
example spec is drawn through pid_from_spec's code and read back by the
graph builder, which never sees the spec. The runner, the chart and the
doc-number gate now default to v4; --matrix v3 / v2 reproduce the earlier
sets, and tests/test_benchmark_v3.py labels its full-matrix run "v3"
explicitly now that the default has moved.

The plan's adapter check expected the two unnumbered lines to come back
with no line number; draw_line builds one from the default number_format
(bare sequence when size/service/spec/insulation are empty), so the task
asserts the two authored numbers on the two process lines and sequence-
built XDATA numbers on the other two instead.

The published A/B report still covers 26 checks; Task 21 re-runs it
against v1.5.1, which is what clears the remaining doc-number drift.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd

tests/test_benchmark_v3.py

@@ -100,7 +100,7 @@ async def test_each_new_task_passes_on_the_headless_backend(task, tmp_path):
 
 @pytest.mark.asyncio
 async def test_the_full_v3_matrix_runs_green(tmp_path):
-    report = await run_tasks(AutoCADMCPProAdapter(), TASKS_V3, tmp_path, timeout=180.0)
+    report = await run_tasks(AutoCADMCPProAdapter(), TASKS_V3, tmp_path, timeout=180.0, matrix="v3")
 
     assert report["summary"]["attempted"] == 15
     assert report["summary"]["passed"] == 15, [

tests/test_benchmark_v4.py

@@ -0,0 +1,35 @@
+"""Track A — the v4 task matrix.
+
+v4 adds one task, ``pid_roundtrip``: draw a P&ID through the same code the
+tools call and read it back through the graph builder, so the edge count, the
+dangling count and the instrument index are each derived independently of the
+drawing code. The published competitor reports were never asked this question
+and the chart shows them ``not_run`` — the same rule v3 set for its five.
+"""
+
+from __future__ import annotations
+
+from benchmarks.tasks_v3 import TASKS_V3
+from benchmarks.tasks_v4 import DEFAULT_MATRIX, MATRICES, NEW_TASKS_V4, TASKS_V4, task_by_id
+
+
+def test_v4_extends_v3_without_touching_it():
+    assert TASKS_V4[: len(TASKS_V3)] == TASKS_V3
+    assert [t.task_id for t in NEW_TASKS_V4] == ["pid_roundtrip"]
+    assert MATRICES["v3"] == TASKS_V3 and MATRICES["v4"] == TASKS_V4 and DEFAULT_MATRIX == "v4"
+    assert task_by_id("pid_roundtrip").category == "pid"
+
+
+def test_the_adapter_implements_every_v4_task():
+    from benchmarks.adapters.autocad_mcp_pro import AutoCADMCPProAdapter
+
+    for task in TASKS_V4:
+        assert hasattr(AutoCADMCPProAdapter, f"_task_{task.task_id}"), task.task_id
+
+
+def test_correctness_suite_has_the_pid_checks():
+    from benchmarks.correctness_suite import CHECKS
+
+    for name in ("pid_block_define_attdef_roundtrip", "pid_tag_parse_fic", "pid_graph_edge_count"):
+        assert CHECKS[name][1] == "P&ID"
+    assert len(CHECKS) == 29