bench: matrix v6 adds arch_roundtrip; four architectural correctness checks; the live arch smoke

The evidence for track F, in the shape tracks A, E and B + G used.

- benchmarks/tasks_v6.py: 19 tasks, DEFAULT_MATRIX = "v6"; v5 to v2 stay
  addressable. arch_roundtrip draws the example plan with
  arch_plan_from_spec and reads it back without the spec: rooms_detect must
  find each labelled room within 0.1 % of its label and of the net floor
  computed by hand (4825 x 5750 and 3825 x 5750), the schedules must list
  D1, D2, W1, W2, and the plan is gated on a zero-issue critique and a
  finalize score of at least 90. A test removes one room label and the gate
  fails naming arch_room_unlabelled.
- Four correctness checks, every number worked out by hand in the docstring:
  L / T / X junction corners and wall areas, a 4 x 5 m room labelled 20.00 m2
  rather than its 21.84 m2 axis area, a door interrupting both faces, and a
  plan of plain lines read as 20 and 15 m2 at confidence 0.6. The published
  A/B report is re-run over 43 checks: 26 / 43 -> 43 / 43, zero regressed.
- scripts/smoke_arch_com.py runs the whole plan once on a live seat and
  closes every document it opens; the CHANGELOG records what it returned.
- The token suite measures a TOOL_PACKS=core,arch row; check_doc_numbers
  derives the task count from the v6 matrix; CLAUDE.md, both READMEs and
  the spec status line say what shipped.
- fix(com): the first live smoke exited 1 - the room reader found 0 wall
  segments. Measured on AutoCAD 2026 (2026-09-23): with a makepy cache,
  ModelSpace.Item(i) returns the gen_py IAcadEntity wrapper
  (type(item).__name__ == "IAcadEntity") and item.StartPoint on an
  AcDbLine raises AttributeError, so every entity_list row lost its
  type-specific properties (28 wall LINEs, 0 with start/end). _entity_info
  now re-dispatches exactly that wrapper through _com_unnarrow; after the
  fix 38 of 53 rows carry start/end and the smoke exits 0 with both rooms
  at 27 743 750 / 21 993 750 mm2 and 0 critique issues. Re-dispatch
  measured at ~1.7 ms per entity (dynamic vs gencache alike).

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

benchmarks/results/published/ab-v1.5.1-vs-v1.6.0-dev.json

@@ -1,12 +1,12 @@
 {
   "summary": {
     "baseline_ref": "v1.5.1",
-    "total": 39,
+    "total": 43,
     "old_pass": 26,
-    "new_pass": 39,
-    "old_pct": 66.7,
+    "new_pass": 43,
+    "old_pct": 60.5,
     "new_pct": 100.0,
-    "fixed": 13,
+    "fixed": 17,
     "regressed": 0
   },
   "rows": [
@@ -243,6 +243,30 @@
       "category": "Sheet",
       "old": "miss",
       "new": "pass"
+    },
+    {
+      "check": "arch_junction_l_t_x",
+      "category": "Architecture",
+      "old": "miss",
+      "new": "pass"
+    },
+    {
+      "check": "arch_room_area_net",
+      "category": "Architecture",
+      "old": "miss",
+      "new": "pass"
+    },
+    {
+      "check": "arch_opening_cuts_wall",
+      "category": "Architecture",
+      "old": "miss",
+      "new": "pass"
+    },
+    {
+      "check": "arch_rooms_detect_foreign",
+      "category": "Architecture",
+      "old": "miss",
+      "new": "pass"
     }
   ]
 }