merge: track H group N

The merge agent stopped this branch on an add/add conflict it had not been
told to expect: groups U and N each created tests/test_understand_tools.py.
Resolved by hand:
- tests/test_understand_tools.py stays U's (the drawing_understand wire
  tests), and N's takeoff wire tests move whole to
  tests/test_understand_takeoff_tools.py. Each file keeps its own client
  fixture: U's opens a fresh document, N's reads files only.
- server.py: SECTION 26 (4 tools, U then D) is kept as merged, and SECTION
  27 (Plant Takeoffs, 2 tools) follows it whole, above the RESOURCES
  banner.
- discovery/aliases.py: additive; the two takeoff records follow the four
  readers.
- tests/test_tool_registry.py: all three branches' paragraphs are kept.
  The snapshot is recomputed from the live registry: analysis 18, 247
  tools. Task 11 ranks `understand` and `plant`.
- docs/tool-inventory.json regenerated (247 tools, 26 groups); README
  counts are 247 registered / 242 advertised. The collected-tests figure
  is left to Task 11.

ruff check passes. Suite: 4919 passed, 1 xfailed. The one deselected test
is the collected-tests figure.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd

tests/test_understand_takeoff_tools.py

@@ -0,0 +1,142 @@
+"""pipe_takeoff and cable_takeoff over the MCP wire, on the synthetic plant pair - never on a
+client drawing."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import pytest
+import pytest_asyncio
+from fastmcp import Client
+
+import server
+from tests.fixtures.plant_pair import build_plant_pair
+
+pytestmark = pytest.mark.asyncio
+
+CSV_NAMES = [
+    "takeoff_metraj.csv",
+    "takeoff_ozet.csv",
+    "takeoff_kontrol.csv",
+    "takeoff_metodoloji.csv",
+]
+
+
+@pytest_asyncio.fixture
+async def client(monkeypatch):
+    """In-memory client on the headless engine - never the operator's AutoCAD."""
+    monkeypatch.setenv("AUTOCAD_MCP_BACKEND", "ezdxf")
+    async with Client(server.mcp) as connected:
+        status = (await connected.call_tool("system_status", {})).structured_content or {}
+        assert status.get("backend") == "ezdxf", "these tests must never touch live AutoCAD"
+        yield connected
+
+
+@pytest.fixture
+def plant(tmp_path):
+    return build_plant_pair(tmp_path)
+
+
+async def test_pipe_takeoff_measures_on_the_layout_and_writes_the_workbook(client, plant, tmp_path):
+    output = tmp_path / "takeoff.xlsx"
+    arguments = {
+        "pid_path": plant["pid"],
+        "layout_path": plant["layout"],
+        "output": str(output),
+        "lang": "tr",
+    }
+    result = (await client.call_tool("pipe_takeoff", arguments)).structured_content
+    assert result["length_source"] == "layout"
+    assert result["scale"]["verdict"] == plant["scale_verdict"]
+    files = result["files"]
+    assert [Path(p).name for p in files["csv"]] == CSV_NAMES
+    assert all(Path(p).exists() for p in files["csv"])
+    if files["xlsx"] is None:
+        assert files["refused"]["capability"] == "xlsx_write"
+    else:
+        assert Path(files["xlsx"]) == output
+        assert output.exists()
+
+
+async def test_pid_lengths_on_the_schematic_pid_are_refused_without_force(client, plant):
+    arguments = {"pid_path": plant["pid"], "layout_path": plant["layout"], "length_source": "pid"}
+    result = await client.call_tool("pipe_takeoff", arguments, raise_on_error=False)
+    assert result.is_error is True
+    text = result.content[0].text
+    assert "the scale check calls this P&ID schematic" in text
+    assert "force=True" in text
+
+
+async def test_force_measures_on_the_pid_and_marks_it_unverified(client, plant):
+    arguments = {
+        "pid_path": plant["pid"],
+        "layout_path": plant["layout"],
+        "length_source": "pid",
+        "force": True,
+    }
+    result = (await client.call_tool("pipe_takeoff", arguments)).structured_content
+    assert (result["length_source"], result["scale_verified"]) == ("pid", False)
+    assert result["files"] is None  # no output named, nothing written
+
+
+async def test_an_unknown_language_is_refused_before_anything_is_read(client, tmp_path):
+    arguments = {"pid_path": str(tmp_path / "never_read.dxf"), "lang": "de"}
+    result = await client.call_tool("pipe_takeoff", arguments, raise_on_error=False)
+    assert result.is_error is True
+    assert "lang: 'de' unknown; choose from tr, en, ru" in result.content[0].text
+
+
+async def test_the_drawings_are_never_modified(client, plant, tmp_path):
+    before = {key: Path(plant[key]).read_bytes() for key in ("pid", "layout")}
+    arguments = {
+        "pid_path": plant["pid"],
+        "layout_path": plant["layout"],
+        "output": str(tmp_path / "t.xlsx"),
+    }
+    await client.call_tool("pipe_takeoff", arguments)
+    assert {key: Path(plant[key]).read_bytes() for key in ("pid", "layout")} == before
+
+
+async def test_the_tool_says_it_writes_a_file_and_destroys_nothing(client):
+    tools = {tool.name: tool for tool in await client.list_tools()}
+    annotations = tools["pipe_takeoff"].annotations
+    assert annotations.readOnlyHint is False
+    assert annotations.destructiveHint is False
+
+
+async def test_cable_takeoff_gives_every_synthetic_load_its_rounded_cable(client, plant, tmp_path):
+    arguments = {
+        "pid_path": plant["pid"],
+        "layout_path": plant["layout"],
+        "output": str(tmp_path / "cables.xlsx"),
+        "lang": "ru",
+    }
+    result = (await client.call_tool("cable_takeoff", arguments)).structured_content
+    rows = {row["tag"]: row for row in result["rows"]}
+    for expected in plant["cable_rows"]:
+        assert rows[expected["tag"]]["cable_m"] == expected["roundup_m"], expected["tag"]
+    assert Path(result["files"]["csv"][0]).name == "cables_metraj.csv"
+
+
+async def test_cable_takeoff_without_a_layout_leaves_every_length_empty(client, plant):
+    result = (
+        await client.call_tool("cable_takeoff", {"pid_path": plant["pid"]})
+    ).structured_content
+    assert result["rows"], "the synthetic P&ID carries electrical loads"
+    assert all(row["cable_m"] is None for row in result["rows"])
+    no_layout = {item["tag"] for item in result["open_items"] if item["item"] == "no_layout"}
+    assert no_layout == {row["tag"] for row in result["rows"]}
+
+
+async def test_a_malformed_section_rule_is_refused_by_path(client, plant):
+    arguments = {"pid_path": plant["pid"], "section_rules": [{"max_kw": 5}]}
+    result = await client.call_tool("cable_takeoff", arguments, raise_on_error=False)
+    assert result.is_error is True
+    assert "section_rules[0].section: expected a non-empty text" in result.content[0].text
+
+
+async def test_the_cable_tool_says_it_writes_a_file_and_destroys_nothing(client):
+    tools = {tool.name: tool for tool in await client.list_tools()}
+    annotations = tools["cable_takeoff"].annotations
+    assert annotations.readOnlyHint is False
+    assert annotations.destructiveHint is False