fix(datasources): preserve governed CSV originals and fresh detail state

Release v0.1.26. Coordinated integrity review: GovOPlaN/govoplan-core#298.

tests/test_migrations.py

@@ -14,6 +14,47 @@ from govoplan_datasources.backend.manifest import get_manifest
 
 
 class DatasourceMigrationTests(unittest.TestCase):
+    def test_csv_evidence_upgrade_preserves_legacy_rows_and_fingerprints(self) -> None:
+        with tempfile.TemporaryDirectory(prefix="govoplan-datasources-csv-migration-") as directory:
+            url = f"sqlite:///{Path(directory) / 'datasources.db'}"
+            config = self._config(url)
+            command.upgrade(config, "d1a7c3e9f5b2")
+            engine = create_engine(url)
+            try:
+                metadata = MetaData()
+                tables = {name: Table(name, metadata, autoload_with=engine) for name in (
+                    "datasource_catalogue", "datasource_stages", "datasource_materializations",
+                )}
+                now = datetime.now(UTC)
+                common = dict(tenant_id="tenant-1", schema=[], fingerprint="a" * 64,
+                              metadata={"retained": True}, provenance={}, created_at=now, updated_at=now)
+                with engine.begin() as connection:
+                    connection.execute(tables["datasource_catalogue"].insert().values(
+                        **common, id="legacy-source", source_name="legacy", name="Legacy", kind="upload",
+                        mode="static", shape="tabular", status="active", schema_version=1,
+                    ))
+                    connection.execute(tables["datasource_stages"].insert().values(
+                        **common, id="legacy-stage", source_name="staged", name="Staged", kind="upload",
+                        mode="static", shape="tabular", state="ready", rows=[{"id": 1}],
+                        row_count=1, byte_count=10, validation={}, governance={}, approval={},
+                    ))
+                    connection.execute(tables["datasource_materializations"].insert().values(
+                        **common, id="legacy-materialization", datasource_id="legacy-source", revision=1,
+                        state="published", schema_version=1, rows=[{"id": 1}], row_count=1,
+                        byte_count=10, governance_snapshot={},
+                    ))
+                    before = {name: dict(connection.execute(select(table)).mappings().one()) for name, table in tables.items()}
+                command.upgrade(config, "e2b8d4a0f6c3")
+                with engine.connect() as connection:
+                    for name in tables:
+                        upgraded = Table(name, MetaData(), autoload_with=connection)
+                        after = dict(connection.execute(select(upgraded)).mappings().one())
+                        if name != "datasource_catalogue":
+                            self.assertIsNone(after.pop("csv_source"))
+                        self.assertEqual(before[name], after)
+            finally:
+                engine.dispose()
+
     @staticmethod
     def _config(url: str):
         return alembic_config(
@@ -34,7 +75,7 @@ class DatasourceMigrationTests(unittest.TestCase):
             try:
                 with engine.connect() as connection:
                     self.assertIn(
-                        "d1a7c3e9f5b2",
+                        "e2b8d4a0f6c3",
                         set(MigrationContext.configure(connection).get_current_heads()),
                     )
                     catalogue_columns = {