fix(understand): a network layer holds lines — valve, pump and annotation layers are no pipes

The field test ran the takeoffs on a real P&ID pair, kept outside the
repository. It showed that the default network layers took every layer the
vocabulary files under piping or electrical. That included the valve layers
(KLEPPEN, Valve_*), the pump layers (a "product pumps" layer reads as
product), and annotation layers such as pipe sizes, materials and valve
numbers. Symbol outlines and leader lines became pipe runs.

vocab.is_network_layer is now the one rule. A layer is a network layer when
it is piping or electrical at 0.9, its name names no equipment
(equipment_kind: valve, pump, tank, motor, panel, reducer), and it names no
annotation (sizes, materials, numbers, hatching, or an annotation word).
build_network's default layers, drawing_topology_check and the topo_*
focuses all use it, so they agree on which lines are the network.

Sixteen parametrized cases pin it, across symbol, annotation, pipe and cable
layers.

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

engineering/understand/vocab.py

@@ -32,6 +32,7 @@ __all__ = [
     "classify_layer",
     "equipment_kind",
     "fold",
+    "is_network_layer",
     "room_label",
     "supply_return",
 ]
@@ -438,6 +439,43 @@ def room_label(text: str | None) -> dict | None:
     return None
 
 
+#: Words that make a piping or electrical layer hold annotation, not lines: pipe
+#: sizes, materials, valve or line numbers, hatching. Matched like every other
+#: keyword here (a word of five letters or more anywhere in the name).
+_NOT_A_LINE_WORDS = (
+    ("annotation", "diameter", "en"),
+    ("annotation", "sizes", "en"),
+    ("annotation", "size", "en"),
+    ("annotation", "material", "en"),
+    ("annotation", "number", "en"),
+    ("annotation", "nummer", "nl"),
+    ("annotation", "arcering", "nl"),
+    ("annotation", "hatch", "en"),
+)
+
+
+def is_network_layer(name: str | None) -> bool:
+    """A layer whose lines are pipes or cables.
+
+    `classify_layer` files it under piping or electrical at 0.9, and its name
+    says neither that it holds symbols - a valve, pump, tank, motor, panel or
+    reducer (`equipment_kind`), whose outlines are no pipe - nor that it holds
+    annotation: sizes, materials, numbers, hatching, or an annotation word.
+    Field P&IDs keep valves and pumps on their own layers (``KLEPPEN``,
+    ``PRODUCT PUMPS``) that a service keyword alone would read as piping.
+    """
+    meaning = classify_layer(name)
+    if meaning["discipline"] not in ("piping", "electrical") or meaning["confidence"] < DIRECT:
+        return False
+    if equipment_kind(name) is not None:
+        return False
+    folded = fold(name)
+    if _first(_NOT_A_LINE_WORDS, folded) is not None:
+        return False
+    annotation = [row for row in _DISCIPLINE_WORDS if row[0] == "annotation"]
+    return _first(annotation, folded) is None
+
+
 def equipment_kind(block_name: str | None) -> dict | None:
     """The kind of equipment a block name says it is: ``{"kind", "keyword", "language"}``.