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_packs.py

@@ -246,7 +246,7 @@ async def test_the_three_track_e_sections_file_under_their_own_groups():
     assert set(groups["environment"]) == SETTINGS_TOOLS
     assert set(groups["mechanical"]) == MECH_TOOLS
     assert set(groups["sheet"]) == SHEET_TOOLS
-    assert len(groups) == 25
+    assert len(groups) == 26  # + architecture (SECTION 25, track F)
 
 
 async def test_system_about_reports_packs():