test(live): retire the qwacback equivalence test; the swap is done

tests/README.md

@@ -25,12 +25,12 @@ everything that needs a JVM, an external oracle, or a running engine.
 | XLSForm fixture inputs are valid XLSForm | external oracle ([pyxform](https://github.com/XLSForm/pyxform)) | pytest — `tests/validation/test_xlsform_pyxform.py` |
 | LimeSurvey accepts the blessed TSV snapshots | live LimeSurvey (docker) | pytest — `tests/live/limesurvey/test_registry_entities.py` |
 | What LimeSurvey *stores* when a respondent answers | live LimeSurvey (docker) + Playwright | pytest — `tests/live/limesurvey/test_response_roundtrip.py` |
-| qwacback's Go converter emits the same DDI shape as `buildDdiXml` | live qwacback (docker) | pytest — `tests/live/qwacback/test_qwacback_equivalence.py` |
 
-qwacback still runs its own Go XLSForm → DDI converter. It plans to replace it
-with this library ([qwacback#3](https://github.com/CorrelAid/qwacback/issues/3)), and the
-equivalence test is the parity check for that swap. After the swap it compares
-the library with itself and can go.
+qwacback converts XLSForm → DDI with this library since
+[qwacback#3](https://github.com/CorrelAid/qwacback/issues/3) (a `ddi-emitter`
+sidecar). The qwacback equivalence test that guarded that swap (ported from
+survey2ddi in formtransform#14) was retired afterwards: it compared the library
+with itself. qwacback keeps its own equivalence check for its wiring (`scripts/equivalence-test.mjs`, `internal/converter/ddi_client_test.go` there).
 
 ## Layout
 
@@ -65,9 +65,6 @@ tests/
       answers/<slug>.json                   #   what the respondent enters
       expected/<slug>.json                  #   blessed exported response
       output/                               #   generated TSVs (gitignored)
-    qwacback/
-      docker-compose.yml                    #   qwacback alone (public ghcr image; QWACBACK_IMAGE overrides)
-      test_qwacback_equivalence.py          #   same XLSForm → buildDdiXml vs. qwacback, DDI shape compared
       build_ddi.mjs                         #   buildDdiXml from dist/ over stdin/stdout
   fixtures/surveys/<name>/                  # one folder per whole survey, like a registry entity
     xlsform.json | xlsform.xlsx              #   authored source
@@ -183,21 +180,6 @@ one — a note stores nothing, and the blessed snapshot records that).
 Needs node + Playwright/Chromium on top of the docker stack; skips if Playwright
 is not resolvable (locally or globally).
 
-### qwacback equivalence (`tests/live/qwacback/test_qwacback_equivalence.py`)
-
-Ported from survey2ddi (formtransform#14). For every answer type qwacback
-supports, the same XLSForm goes through `buildDdiXml` and qwacback's
-`POST /api/convert/xlsform-to-ddi`, and the `<var>`/`<varGrp>` shapes are
-compared. qwacback returns a bare `<var>` or `<varGrp>` when there's only one,
-so the test wraps it in a `<dataDscr>`. `note` is a strict xfail, by design:
-formtransform emits no `<var>` for a note.
-
-The fixture starts qwacback from its own compose file, or uses `QWACBACK_URL`.
-It pulls the public `ghcr.io/correlaid/qwacback:latest`. To test an unreleased
-qwacback, build it (`docker build -t qwacback:local ../qwacback`) and set
-`QWACBACK_IMAGE=qwacback:local`. If the image can't be pulled, the tests skip
-with that reason.
-
 ## Running
 
 ```bash