docs: replace schema-refresh docs with a rerunnable script

README.md pointed at .plans/index.md, which isn't committed to the
repo. Add refresh_schema.py to download the vendored QTI/W3C/MathML/SSML
XSDs and reapply the local schemaLocation rewrites repeatably, and point
the README at it instead.

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

Author: rtibblesbot

contentcuration/contentcuration/utils/assessment/qti/schema/README.md

@@ -19,6 +19,11 @@ have been rewritten to local relative filenames so the schema compiles with no n
 access at runtime — required since bulk publish and ricecooker upload validate many items
 per run. Do not restore the absolute URLs.
 
-To refresh to a newer QTI point release: re-download each file above, re-apply the
-`schemaLocation` rewrites documented in `.plans/index.md` (issue #6005) or by diffing
-against the current vendored copy, then re-run the full `test_validation.py` suite.
+To refresh to a newer QTI point release, run `refresh_schema.py` (re-downloads each
+file above and re-applies the `schemaLocation` rewrites), then re-run the full
+`test_validation.py` suite:
+
+```
+python contentcuration/contentcuration/utils/assessment/qti/schema/refresh_schema.py
+pytest contentcuration/contentcuration/tests/utils/qti/test_validation.py -v
+```

contentcuration/contentcuration/utils/assessment/qti/schema/refresh_schema.py

@@ -0,0 +1,91 @@
+"""Re-vendor the QTI 3.0 item XSD schema tree.
+
+Downloads the QTI-item XSD and its W3C/MathML/SSML dependencies, then
+rewrites their `schemaLocation` attributes from absolute
+`https://purl.imsglobal.org/...` URLs to local relative filenames so the
+schema tree compiles with no network access at runtime.
+
+Usage: python refresh_schema.py
+(Run from any directory; writes into the `xsd/` subdirectory next to this
+script.) Afterwards, re-run the validation test suite:
+
+    pytest contentcuration/contentcuration/tests/utils/qti/test_validation.py -v
+"""
+import socket
+from pathlib import Path
+
+import requests
+from lxml import etree
+
+
+XSD_DIR = Path(__file__).parent / "xsd"
+
+SOURCES = {
+    "imsqti_itemv3p0p1_v1p0.xsd": "https://purl.imsglobal.org/spec/qti/v3p0/schema/xsd/imsqti_itemv3p0p1_v1p0.xsd",
+    "xml.xsd": "https://purl.imsglobal.org/spec/w3/2001/schema/xsd/xml.xsd",
+    "XInclude.xsd": "https://purl.imsglobal.org/spec/w3/2001/schema/xsd/XInclude.xsd",
+    "mathml3.xsd": "https://purl.imsglobal.org/spec/mathml/v3p0/schema/xsd/mathml3.xsd",
+    "mathml3-content.xsd": "https://purl.imsglobal.org/spec/mathml/v3p0/schema/xsd/mathml3-content.xsd",
+    "mathml3-presentation.xsd": "https://purl.imsglobal.org/spec/mathml/v3p0/schema/xsd/mathml3-presentation.xsd",
+    "mathml3-common.xsd": "https://purl.imsglobal.org/spec/mathml/v3p0/schema/xsd/mathml3-common.xsd",
+    "mathml3-strict-content.xsd": "https://purl.imsglobal.org/spec/mathml/v3p0/schema/xsd/mathml3-strict-content.xsd",
+    "ssmlv1p1-core.xsd": "https://purl.imsglobal.org/spec/ssml/v1p1/schema/xsd/ssmlv1p1-core.xsd",
+    "synthesis-nonamespace.xsd": "https://purl.imsglobal.org/spec/ssml/v1p1/schema/xsd/synthesis-nonamespace.xsd",
+}
+
+# schemaLocation rewrites: file -> its dependencies (keys into SOURCES),
+# each rewritten from the dependency's absolute URL to its local filename.
+REWRITES = {
+    "imsqti_itemv3p0p1_v1p0.xsd": [
+        "xml.xsd",
+        "XInclude.xsd",
+        "mathml3.xsd",
+        "ssmlv1p1-core.xsd",
+    ],
+    "ssmlv1p1-core.xsd": ["xml.xsd"],
+    "synthesis-nonamespace.xsd": ["xml.xsd"],
+}
+
+
+def download():
+    XSD_DIR.mkdir(parents=True, exist_ok=True)
+    for filename, url in SOURCES.items():
+        response = requests.get(url, timeout=30)
+        response.raise_for_status()
+        (XSD_DIR / filename).write_bytes(response.content)
+
+
+def rewrite_schema_locations():
+    for filename, deps in REWRITES.items():
+        path = XSD_DIR / filename
+        text = path.read_text()
+        for dep in deps:
+            old = 'schemaLocation="%s"' % SOURCES[dep]
+            new = 'schemaLocation="%s"' % dep
+            assert old in text, "%r not found in %s" % (old, filename)
+            text = text.replace(old, new)
+        path.write_text(text)
+
+
+def verify_compiles_offline():
+    real_socket = socket.socket
+
+    def _blocked(*args, **kwargs):
+        raise RuntimeError("network access attempted while compiling vendored schema")
+
+    socket.socket = _blocked
+    try:
+        etree.XMLSchema(etree.parse(str(XSD_DIR / "imsqti_itemv3p0p1_v1p0.xsd")))
+    finally:
+        socket.socket = real_socket
+
+
+def main():
+    download()
+    rewrite_schema_locations()
+    verify_compiles_offline()
+    print("Vendored schema refreshed in %s" % XSD_DIR)  # noqa: T201
+
+
+if __name__ == "__main__":
+    main()