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

docs/tool-inventory.json

@@ -3,13 +3,14 @@
   "schema_version": 1,
   "package_version": "1.5.1",
   "totals": {
-    "tools": 229,
+    "tools": 233,
     "resources": 8,
     "prompts": 5,
-    "groups": 25
+    "groups": 26
   },
   "groups": {
     "analysis": 12,
+    "architecture": 4,
     "batch": 3,
     "blocks": 9,
     "corner_ops": 4,
@@ -180,6 +181,62 @@
         "readOnlyHint": true
       }
     },
+    {
+      "name": "arch_dimension_chains",
+      "group": "architecture",
+      "cost": "mutate",
+      "summary": "Dimension the plan's facades: openings, walls and overall chains outside each side.",
+      "tags": [
+        "arch",
+        "dimension"
+      ],
+      "annotations": {
+        "title": "Architecture: Dimension Chains",
+        "destructiveHint": false
+      }
+    },
+    {
+      "name": "arch_opening",
+      "group": "architecture",
+      "cost": "mutate",
+      "summary": "Host a door or a window in a drawn wall by distance along it; the wall is cut.",
+      "tags": [
+        "arch",
+        "create"
+      ],
+      "annotations": {
+        "title": "Architecture: Door / Window",
+        "destructiveHint": false
+      }
+    },
+    {
+      "name": "arch_stair",
+      "group": "architecture",
+      "cost": "mutate",
+      "summary": "Draw a straight, L or U stair in plan and report its Blondel step rule.",
+      "tags": [
+        "arch",
+        "create"
+      ],
+      "annotations": {
+        "title": "Architecture: Stair",
+        "destructiveHint": false
+      }
+    },
+    {
+      "name": "arch_wall",
+      "group": "architecture",
+      "cost": "mutate",
+      "summary": "Add walls to the plan: clean L/T/X junctions, cut openings, material poché.",
+      "tags": [
+        "arch",
+        "create"
+      ],
+      "annotations": {
+        "title": "Architecture: Wall",
+        "destructiveHint": false
+      }
+    },
     {
       "name": "balloon_add",
       "group": "sheet",