feat(arch): the plan model and its foundation - layers, materials, EN/TR, two generalisations

Track F starts here; the three group branches are cut from this commit.

- engineering/arch/model.py: Wall, Opening, Stair and Room as frozen
  dataclasses, and every refusal of spec 4 before anything is drawn, by path
  (walls[2].thickness): finite positive numbers, an axis of at least two
  distinct points with no zero-length segment, an arc segment refused by name
  rather than approximated, an opening on an unknown wall, past its wall,
  across an axis vertex or overlapping another (both ids named), an unknown
  material, and a typed room area - areas are measured, never typed. The
  plan travels as ACADMCP_ARCH XDATA; an opening's door/window kind and a
  stair's straight/l/u kind ride beside the payload kind as opening_kind /
  stair_kind, because one key cannot hold both.
- engineering/arch/layers.py: the arch set - thirteen ISO 13567-style layers
  with ISO 128 lineweights only (0.05 mm on the construction scratch layer,
  as every set in this repository) - and ARCH_ROLE_LAYER, the one place a
  role becomes a layer. Registered in engineering/layers.py last, which is
  what keeps the engineering.layers <-> engineering.arch import cycle closed.
- engineering/arch/materials.py: eight wall materials, one pattern each,
  every row citing its source: ANSI31 for brick (ISO 128-50 general hatching,
  acadiso.pat's own "Iron, Brick, Stone masonry"), AAC as ANSI31 at twice the
  spacing (a repository convention, and it says so), AR-CONC / AR-SAND as
  AutoCAD patterns, and the JIS A 0150 RC / stone / wood symbols. Reinforced
  concrete cannot be ANSI31 and AR-CONC in one HATCH, so it takes the one
  symbol that names it. Periods on a 1:50 sheet are recomputed from ezdxf's
  own pattern definitions by the tests. normalise_material is the one reading
  of a material name, shared by the model and wall_hatch, so the model never
  refuses "Reinforced Concrete" that the hatch table resolves.
- engineering/arch/lang.py: EN / TR vocabulary, D/W and K/P tag prefixes, and
  the decimal comma for lang="tr" (24,50 m2).
- draw_prims(role_layer=) and the XDATA codec's app_id= / kinds=: both
  generalised with the mechanical defaults, and the mechanical suite passes
  unchanged against them - that is the regression gate.

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

engineering/layers.py

@@ -120,7 +120,7 @@ async def apply_layer_set(
     backend: AutoCADBackend,
     standard: str = "mech",
 ) -> dict[str, str]:
-    """Idempotently apply a named layer set ('mech', 'pid', 'iso13567')."""
+    """Idempotently apply a named layer set ('mech', 'pid', 'iso13567', 'arch')."""
     layer_set = LAYER_SET_REGISTRY.get(standard)
     if layer_set is None:
         raise RuntimeError(
@@ -150,3 +150,16 @@ async def apply_layer_set(
         except Exception as exc:
             results[name] = f"failed: {exc}"
     return results
+
+
+# ── the architectural set (track F) ─────────────────────────────────────────
+# The rows live with the plan model (engineering/arch/layers.py), where
+# ARCH_ROLE_LAYER maps each role onto them. Registered last, after every name
+# above exists: importing engineering.arch runs its package __init__, which
+# pulls in the mechanical codec - and, once track F is merged, the wall engine
+# - and those import from this module. A partially initialised
+# engineering.layers must already hold every name they ask for.
+from engineering.arch.layers import ARCH_LAYER_ROLES, ARCH_LAYERS  # noqa: E402
+
+LAYER_SET_REGISTRY["arch"] = ARCH_LAYERS
+LAYER_ROLES["arch"] = dict(ARCH_LAYER_ROLES)