bench: matrix v7 adds takeoff_roundtrip and understand_foreign; five understanding checks; the live smoke and the field-test script

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

- benchmarks/tasks_v7.py: 21 tasks, DEFAULT_MATRIX = "v7"; v6 to v2 stay
  addressable. Both new tasks read the synthetic plant pair and nothing
  else. takeoff_roundtrip: the P&ID called schematic, every routable run's
  layout length equal to the rectilinear MST of its tags, sizes and services
  as drawn (a return drawn on the supply layer included), the cable metres
  rounded up after the allowance, an unstated power left empty.
  understand_foreign: inches over millimetres flagged, the stray entity found
  by handle, two plan copies separated, five layers classified. A test breaks
  each input and watches its gate fail by name.
- Five correctness checks, every number worked out by hand in its docstring;
  the published A/B report is re-run over 48 checks: 26 / 48 -> 48 / 48,
  zero regressed.
- scripts/smoke_understand_com.py reads the pair through the live engine -
  snapshots, the DWG route, both takeoffs and a diff - and closes every
  document it opens; the CHANGELOG records what it returned.
  scripts/field_test_takeoff.py runs the takeoffs on a user's own files,
  refuses to write inside the repository and prints no quantity by default.
- The README token table is remeasured; check_doc_numbers derives the task
  count from the v7 matrix; CLAUDE.md, both READMEs, the CHANGELOG and the
  spec status line say what shipped.

One reader defect found on the way: describe.tag_occurrences read a wiring
callout ("Wiring to CP-2") as a place its panel is written, so the scale
check called CP-2 ambiguous and read "Wiring to CP1" as a phantom tag CP1 -
10 tags and 45 pairs (13.3 % within 10 %) where the generator placed 11 and
55 (21.8 %). A callout is no longer a tag occurrence, the rule
network.tag_occurrences already kept; two tests failed before the fix.

The smoke works only in documents it opened from its own temporary folder,
known by full path; it attaches with GetActiveObject only (the backend's
Dispatch fallback would launch AutoCAD), checks in the same COM-thread call
that the active document is its own before each snapshot, the DWG save and
the move, closes its documents with Close(False) and re-activates the
document that was active when it started. No new ActiveX member: Documents,
Item, FullName, ActiveDocument, Activate and Close are the ones the backend
already calls. Measured on AutoCAD 2026 (25.1s): exit 0, model-space types
equal file / live / DWG, export 0.104 s, no document of the run left open.

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

benchmarks/README.md

@@ -127,6 +127,17 @@ result for it.
 
 The competitor reports carry no result for it.
 
+### Matrix v7 (v1.6) — understanding foreign drawings
+
+`tasks_v7.py` keeps the v6 nineteen unchanged and adds track H's evidence, both on the synthetic plant pair of `tests/fixtures/plant_pair.py` (invented names; its truth is computed from the positions it placed, never typed):
+
+| Task | Category | Verified against |
+|---|---|---|
+| `takeoff_roundtrip` | plant | `scale_check(pid, layout)` must say **schematic** (room 1 is a 1.3× stretch, room 2 is rearranged: 21.8 % of the 55 tag pairs within ±10 % of the median ratio); `pipe_rows(..., length_source="auto")` must report all nine runs with the truth's status, each routable run's layout length equal to the rectilinear MST of its tags to a micron (PR1 5500, PR2 13200, CS1 20700 mm, …), its size and service as drawn — the CIP return drawn on the supply layer included — and both sizes across the reducer; `cable_rows` must give M11 / T102 / M12 / T202 their panels, 6900 / 14100 / 15800 / 8000 mm and 9 / 17 / 19 / 10 m after the 20 % allowance, the heater's power empty. `tests/test_benchmark_v7.py` deletes the wiring callouts and the gate names all four loads |
+| `understand_foreign` | understand | `describe(layout)` must infer millimetres and warn about `INSUNITS` (the file says inches), name the stray line's handle in its extents and report two clusters (the plan is drawn twice, 100 m apart); `describe(pid)` must classify `P_product piping`, `P_cipsupplyline`, `P_cipreturnline`, `P_ijswater` and `E_power` as product, CIP supply, CIP return, ice water and electrical. `tests/test_benchmark_v7.py` makes the layout declare millimetres and the units gate fails alone |
+
+The competitor reports carry no result for them.
+
 ## Live competitor lane (v1.4)
 
 Two competitor adapters now execute the exact same task matrix, black-box over
@@ -244,15 +255,15 @@ python benchmarks/compare_versions.py --json results.json
 
 ### Result — this branch (1.6.0-dev) vs v1.5.1 (release gate)
 
-43 checks, ezdxf backend, one subprocess per check. Machine-readable report:
+48 checks, ezdxf backend, one subprocess per check. Machine-readable report:
 [`results/published/ab-v1.5.1-vs-v1.6.0-dev.json`](results/published/ab-v1.5.1-vs-v1.6.0-dev.json).
 
 | Version | Checks passing | Pass rate | Fixed | Regressed |
 |---------|----------------|-----------|-------|-----------|
-| **v1.5.1** (baseline)     | 26 / 43 | 60.5 % | — | — |
-| **v1.6.0-dev** (this branch) | 43 / 43 | 100 % | 17 | **0** |
+| **v1.5.1** (baseline)     | 26 / 48 | 54.2 % | — | — |
+| **v1.6.0-dev** (this branch) | 48 / 48 | 100 % | 22 | **0** |
 
-The seventeen are all `miss → pass` — v1.5.1 has none of the methods. Four are track F: `arch_junction_l_t_x` (L, T and X junction outlines against hand-computed corners and wall areas), `arch_room_area_net` (a 4 × 5 m room between 200 mm walls is labelled 20.00 m², not its 21.84 m² axis area), `arch_opening_cuts_wall` (both faces interrupted across a door, two jambs) and `arch_rooms_detect_foreign` (plain lines on a WALLS layer read as 20 and 15 m² at confidence 0.6, nothing written). Seven
+The twenty-two are all `miss → pass` — v1.5.1 has none of the methods. Five are track H: `scale_check_detects_schematic` (the synthetic P&ID is schematic against its layout; a uniform 2× copy is to scale with factor 2), `pipe_takeoff_rmst_exact` (eight routable runs, each exactly the rectilinear MST of its tags), `cable_takeoff_roundup` (9 / 17 / 19 / 10 m, the unstated power left empty), `diff_detects_known_edits` (five known edits and nothing else) and `topology_known_defects` (one near miss, one crossing, a clean T). Four are track F: `arch_junction_l_t_x` (L, T and X junction outlines against hand-computed corners and wall areas), `arch_room_area_net` (a 4 × 5 m room between 200 mm walls is labelled 20.00 m², not its 21.84 m² axis area), `arch_opening_cuts_wall` (both faces interrupted across a door, two jambs) and `arch_rooms_detect_foreign` (plain lines on a WALLS layer read as 20 and 15 m² at confidence 0.6, nothing written). Seven
 are tracks B and G: `mech_part_roundtrip` (a part read back from its own
 `ACADMCP_MECH` XDATA equals the part drawn), `mech_section_hatch_area` (a
 sleeve 60 long, ⌀40 outside, ⌀20 bore: a full section cuts two 60 × 10 faces,