fix: seven defects an adversarial audit found, and the gates that missed them

Every one of these was reported ok/clean to the caller while being wrong.

Silently wrong numbers
- selection_filter(min_area) read `entity.dxf.get("area", 0.0)` for SOLID,
  TRACE and HATCH, none of which carry that attribute, so every hatch
  measured 0.0. A 1600 mm^2 hatch was excluded by min_area=1.0 while
  `filtered_by` asserted the filter had run, and COM (which reads ActiveX
  .Area) returned a different selection for the same call. It now answers
  from the measurement `entity_measure` uses, so the two cannot disagree.
- Every headless dimension rendered through ezdxf's bare `Standard` style:
  1.0 mm text with a comma decimal marker, against ISO 3098's 2.5 mm minimum
  and ISO 129's point -- while the document header itself said $DIMTXT 2.5.
  `ezdxf.new(setup=True)` is not the fix; measured, it renders a 100 mm
  dimension as "10000". The attributes are now stored explicitly.
- Saving writes `dimrnd = 0.0` onto the Standard style, and ezdxf applies
  `xround(value, dimrnd)` whenever the attribute is present at all --
  `xround(33.333, 0.0)` is 33. So on any reopened file, including one this
  server saved, every dimension was rounded to a whole unit before DIMDEC
  formatted it: a 12.75 mm feature dimensioned 13. AutoCAD means DIMRND 0 as
  *no* rounding; the sentinel is now discarded at every load site, and a real
  0.5 mm rounding is left alone.
- The DIM* header fold gave out-of-range values teeth they did not have when
  they died in the header: dim_decimals=-1 returned ok and then killed the
  next dimension with `ValueError: Format specifier missing precision` from
  inside ezdxf, and 40 printed forty digits of float noise onto the sheet.
  Ranges are now AutoCAD's own (DIMDEC 0-8, DIMZIN 0-15, lengths positive).

Security
- security.py recorded the policy as "sanitize_command and sanitize_lisp each
  have exactly ONE caller ... the policy is scoped to the CHANNEL". The
  premise was false. `_ensure_linetype_loaded` and `ComBackend.linetype_load`
  build `_-LINETYPE _LOAD {name} {file}` and hand it to SendCommand, which
  treats a newline and ';' as segment separators -- so a `linetype=` argument
  carrying either injected further AutoCAD commands, and the 36-verb denylist
  never saw that channel. Guarded with the DXF symbol-name rule (the
  injection characters fall out of it rather than being enumerated) plus
  validate_path for the file argument, which was also the one path-taking
  tool reaching the filesystem unchecked. The policy comment is corrected.

Gates that could not see
- drawing_critique returned zero issues on a quarantined document: all seven
  checks wrapped their backend call in a bare `except Exception`. CLAUDE.md
  rule 7 makes that call the gate an agent is told to trust. Only the
  quarantine now escapes; an ordinary broken check still degrades.
  `_check_dimension_legibility` also read `_doc` directly from the event loop
  thread, missing the gate and performing exactly the unsynchronised access
  the quarantine exists to prevent. `construction_clear` answered
  "deleted: 0" -- there was nothing to clear -- for the same reason.
- The iso128 focus checked layer lineweights only, so a sheet lettered at
  1.0 mm critiqued clean. It now reads the effective dimension height and
  separator, header-then-style, in the order the renderer resolves.
- check_doc_numbers.py derived five values it never checked, and those were
  the ones that had drifted. The collected-test count (README said 1274, the
  tree had 1369) and the A/B pass-rate and Fixed columns are now gated.
- benchmarks/README.md's v1.4.0 table was impossible on its face -- 21
  passing plus 5 fixed is 26, not 24 -- and contradicted the report it
  linked, because `ab-v1.4.0-vs-v1.5.0.json` was regenerated from a tree that
  already carried the dimension fixes and so never measured the v1.5.0 tag.
  Replaced with a real run: ab-v1.4.0-vs-v1.5.1.json, 21/26 -> 26/26.

Release gate
- release.yml ran one ubuntu/3.11 lane, so a Windows-only defect could reach
  PyPI with no Windows job having executed. That is not hypothetical: v1.5.0
  shipped `except pywintypes.com_error` raising NameError wherever pywin32 is
  absent. It now runs the same three lanes as ci.yml, Windows included.

1368 passed, 1 xfailed. ruff clean. Tool inventory and all 16 gated document
numbers match the tree.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/test_com_backend.py

@@ -431,3 +431,53 @@ async def test_a_simple_polyline_is_not_flagged():
     backend = _measure_backend(entity)
 
     assert (await backend.entity_measure("8A5"))["self_intersecting"] is False
+
+
+# ── the member profile, measured on a live AutoCAD 2026 (2026-08-06) ────────
+#
+# Probed on a fresh seat with a throwaway drawing, nothing saved:
+#   AcDbCircle    Area 314.1593  Circumference 62.8319   (no Length, no Coordinates)
+#   AcDbPolyline  Area 1600.0    Length 160.0            Coordinates present
+#   AcDbHatch     Area 942.4778  -- r20 with an r10 island, so pi*(400-100):
+#                                   AutoCAD's hatch area DOES subtract islands
+#   AcDbRegion    Area 1600.0    Perimeter 160.0
+#   AcDb3dSolid   Area ABSENT    Volume 1000.0
+#
+# The last row is the one that matters: ActiveX exposes no `.Area` on a 3DSOLID
+# at all, so "REGION / 3DSOLID area" was half a claim.
+
+
+@pytest.mark.asyncio
+async def test_a_circle_uses_circumference_for_its_perimeter():
+    """Measured: AcDbCircle has `.Circumference` and no `.Length`."""
+    backend = _measure_backend(_Entity("AcDbCircle", Area=314.1593, Circumference=62.8319))
+
+    result = await backend.entity_measure("C01")
+
+    assert result["area"] == pytest.approx(314.1593)
+    assert result["perimeter"] == pytest.approx(62.8319)
+    assert result["perimeter_exact"] is True
+
+
+@pytest.mark.asyncio
+async def test_a_region_uses_perimeter():
+    """Measured: AcDbRegion has `.Perimeter` and no `.Length`."""
+    backend = _measure_backend(_Entity("AcDbRegion", Area=1600.0, Perimeter=160.0))
+
+    result = await backend.entity_measure("R01")
+
+    assert result["area"] == pytest.approx(1600.0)
+    assert result["perimeter"] == pytest.approx(160.0)
+
+
+@pytest.mark.asyncio
+async def test_a_3dsolid_is_refused_by_name_because_activex_has_no_area_for_it():
+    """Measured: AcDb3dSolid exposes Volume and no Area at all.
+
+    The generic "neither an area nor usable vertices" would send the reader
+    hunting for geometry that was never the problem.
+    """
+    backend = _measure_backend(_Entity("AcDb3dSolid", Volume=1000.0))
+
+    with pytest.raises(RuntimeError, match="no surface-area member"):
+        await backend.entity_measure("S01")