fix: close remaining review gaps in vocabulary/deterministic-IRI PR

serialize_to_rdfxml still defaulted entity_type to the bare string
"semantica:Entity" written into an rdf:resource attribute, which isn't
namespace-expanded the way a Turtle angle-bracket or XML element name is -
the same #1101 failure mode, just on the path the original tests didn't
cover. Now uses the full-IRI DEFAULT_ENTITY_TYPE like the Turtle path.

json_exporter.py emits semantica:format and @type: "semantica:KnowledgeGraph",
neither of which was declared in the vocabulary or included in
EMITTED_TERMS, so the "undeclared terms fail the build" guarantee didn't
actually cover them. Both are now declared with rdfs:label/comment and
added to the guard set.

MANIFEST.in didn't mirror the pyproject.toml package-data addition, so a
source-distribution install could ship without the vocabulary file.

The cross-process minting-stability test replaced the subprocess's entire
environment with a POSIX-only PATH, breaking it on Windows and any host
needing other inherited env vars; now overrides only PYTHONHASHSEED on top
of the inherited environment.

Also folds mint_entity_iri/mint_relationship_iri's hand-rolled
hashlib.sha256(...).hexdigest() into the existing hash_data() helper this
file already imports alongside.

229 export and ontology tests pass, including a new regression test for
the RDF/XML default-type fix.

Co-Authored-By: fabio-rovai <fabio@thetesseractacademy.com>

tests/export/test_rdf_exporter_iri_minting.py

@@ -11,6 +11,7 @@ IRI in the scheme ``semantica`` rather than the expansion of the declared
 ``semantica:`` prefix, so it never joined with anything written through it.
 """
 
+import os
 import subprocess
 import sys
 
@@ -45,7 +46,7 @@ def test_minted_entity_iri_is_stable_across_processes():
             capture_output=True,
             text=True,
             check=True,
-            env={"PYTHONHASHSEED": seed, "PATH": "/usr/bin:/bin"},
+            env={**os.environ, "PYTHONHASHSEED": seed},
         ).stdout.strip()
         for seed in ("0", "1", "random")
     }
@@ -88,6 +89,22 @@ def test_default_types_are_written_as_full_iris_in_turtle():
     assert "<semantica:related_to>" not in turtle
 
 
+def test_default_entity_type_is_a_full_iri_in_rdfxml():
+    """RDF/XML's rdf:resource is an attribute value, not a QName context, so a
+
+    prefixed default there (``semantica:Entity``) resolves to the scheme
+    ``semantica`` rather than the declared namespace — the same failure mode
+    fixed for Turtle in #1101, missed here because the original tests only
+    checked Turtle output.
+    """
+    untyped = {"entities": [{"id": "https://example.org/e1", "text": "A"}],
+               "relationships": []}
+    rdfxml = RDFExporter().export_to_rdf(untyped, format="rdfxml")
+
+    assert f'rdf:resource="{DEFAULT_ENTITY_TYPE}"' in rdfxml
+    assert 'rdf:resource="semantica:Entity"' not in rdfxml
+
+
 def test_temporal_minting_uses_either_endpoint_representation():
     """Relationships may carry source/target or source_id/target_id (#1109 review).