feat(understand): the takeoff workbook and pipe_takeoff (SECTION 27 opens)

write_workbook builds the user's takeoff workbook from a result: Metraj (rows
with direct, continuity and unassigned lengths split, the allowance as its
own column, routed / unroutable / grand totals), Ozet (by service, diameter
and room), Kontrol (unassigned diameters and unroutable runs with the
reason) and Metodoloji, generated from the result: sources, the length
source and why, the scale-check verdict with its statistics, the units,
every rule and tolerance, and every warning. Headers and sentences in
Turkish, English or Russian. CSV always, one file per sheet; XLSX with
openpyxl, otherwise the xlsx_write refusal naming the office extra while
the CSV files are still written.

pipe_takeoff reads the P&ID and the layout once each (take_snapshot),
computes in a worker thread and never modifies either drawing. Tagged plant
and analysis; the plant pack is the integration task's. Alias record in
English, Turkish and Russian. Inventory regenerated; README snapshot 242
tools (237 advertised); registry snapshot analysis: 13.

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

tests/test_understand_tools.py

@@ -0,0 +1,103 @@
+"""pipe_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