fix: enforce internal embeddings contract

harness/tests/test_config_resources.py

@@ -106,7 +106,7 @@ roots:
   sessions: {runtime_root / 'sessions'}
   artifacts: {runtime_root / 'artifacts'}
   indexes: {runtime_root / 'indexes'}
-embeddings: {{base_url: http://embedding.invalid, model: embed, dim: 768}}
+embeddings: {{provider: ollama_internal, base_url: http://embedding:11434, model: qwen3-embedding:0.6b, dim: 1024}}
 """)
     monkeypatch.setenv("THT_DATA_ROOT", str(data_root))
 
@@ -204,7 +204,7 @@ dwh:
 vectors:
   type: thoth_vector_http
   writer: {base_url: https://vectors.test/, api_key: writer}
-embeddings: {base_url: http://ollama:11434, dim: 768}
+embeddings: {provider: ollama_internal, base_url: http://embedding:11434, model: qwen3-embedding:0.6b, dim: 1024}
 """
     )
 
@@ -302,6 +302,25 @@ dwh:
         load_config(workspace)
 
 
+def test_rejects_external_top_level_embedding_configuration(tmp_path):
+    workspace = tmp_path / "workspace.yaml"
+    workspace.write_text(
+        """
+dwh:
+  type: postgres_direct
+  connection: {database: analytics, schema: mart, user: reader, password: secret}
+embeddings:
+  provider: openai_compatible
+  base_url: https://embedding.example.test
+  model: text-embedding-3-large
+  dim: 3072
+"""
+    )
+
+    with pytest.raises(ConfigError, match="ollama_internal|provider|base_url|model|1024"):
+        load_config(workspace)
+
+
 def test_builds_typed_evidence_sources_and_keeps_legacy_compatible(tmp_path):
     common = """
 dwh: