feat(arch): SECTION 25 opens - walls, openings, stairs and exterior chains as tools

engineering/arch/draw.py is the only module of the track that touches a
backend. It draws through draw_prims(role_layer=ARCH_ROLE_LAYER) and the
generic contract members, so it runs on both engines as written, and it writes
the plan onto the drawing: each element's ACADMCP_ARCH record on one of its own
entities (a wall's first face line, a door's leaf, a window's frame, a stair's
first riser) and, beside it under ACADMCP_ARCH_H, the handles that element
owns. read_plan reads the records back and never modifies the drawing.

arch_wall computes the whole network before and after the new walls and
redraws only the drawn walls whose outline changes - erasing exactly the
entities they own - and says which under redrawn. arch_opening hosts a door or
a window in a drawn wall found by id and redraws that wall cut; its tag
defaults to the next D1/W1 (K1/P1 in Turkish). A new wall that would leave a
drawn opening uncuttable, and an opening that runs into a junction, are refused
before anything is erased. arch_stair reports the Blondel value; it does not
enforce it.

exterior_chains gives each side up to three rows, nearest first: every jamb in
that facade, both faces of every wall meeting it, and the overall - from the
wall engine's own faces. A row that would only restate a farther one is not
emitted (ISO 129-1: each measurement once). The 10 mm / 8 mm row spacing is a
declared drafting default times the plot scale, not a standard value.

The arch tag is ranked after mech so the four tools file under a new
architecture group; alias records carry WALLADD/MLINE, DOORADD/WINDOWADD and
STAIRADD with English and Turkish shop words. Inventory regenerated; README
snapshot 233 tools (228 advertised) in 26 groups; registry snapshot
architecture: 4.

No new ActiveX member is called. Measured on AutoCAD 2026 in a scratch
document through ComBackend: shell + teed partition, D1 + W1, a straight 17-riser stair
and the bottom chains gave the same 20 wall LINEs (identical endpoints),
9 poche HATCHes, 1+1 door, 4 window lines, 11 dimensions and a read_plan
round trip as the headless engine.

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

tests/test_tool_registry.py

@@ -495,7 +495,7 @@ async def test_tool_groups_is_byte_identical_to_the_source_declared_grouping():
 
 
 async def test_tool_group_sizes_are_unchanged():
-    """Frozen snapshot of the surface (229 tools, 25 groups).
+    """Frozen snapshot of the surface (233 tools, 26 groups).
 
     Taken before @cad_tool landed at 131 tools; `batch` moved 2 -> 3 when
     v1.5.0's `cad_batch` joined `entity_batch_create`/`entity_batch_modify`, and
@@ -581,10 +581,17 @@ async def test_tool_group_sizes_are_unchanged():
     `sheet`, so pack, group and SECTION are one list again: `engineering`
     returned 17 -> 10, `blocks` 11 -> 9, `entity_creation` 19 -> 18 and
     `drawing` 12 -> 11 — every one of them its pre-SECTION-24 value.
+
+    `architecture` appeared with v1.6's track F: SECTION 25 opened with the
+    plan model's wall engine (`arch_wall` / `arch_opening` / `arch_stair` /
+    `arch_dimension_chains`); the `arch` tag is ranked directly after `mech` in
+    `_GROUP_TAG_PRIORITY`, so those tools file under `architecture` rather
+    than under their secondary `create` / `dimension` tags.
     """
     sizes = {label: len(names) for label, names in (await server._tool_groups()).items()}
     assert sizes == {
         "analysis": 12,
+        "architecture": 4,
         "batch": 3,
         "blocks": 9,
         "corner_ops": 4,
@@ -610,4 +617,4 @@ async def test_tool_group_sizes_are_unchanged():
         "validation": 1,
         "view": 4,
     }
-    assert sum(sizes.values()) == 229
+    assert sum(sizes.values()) == 233