fix(core): preserve adapter command contracts

harness/tests/test_schema_introspect_guard.py

@@ -4,6 +4,8 @@ from typer.testing import CliRunner
 
 from tht.cli import app
 from tht.mschema.models import ColumnPhysical, PhysicalSchema, TablePhysical
+from tht.config import ExamplesConfig
+from tht.cli.schema_cmd import _add_examples
 
 
 def _write_catalog(tmp_path):
@@ -68,3 +70,23 @@ def test_render_without_catalog_guides_fallback(tmp_path):
     res = CliRunner().invoke(app, ["schema", "render", "-c", str(cfg)])
     assert res.exit_code == 1
     assert "Esegui prima" in res.output
+
+
+def test_examples_skip_one_unreadable_column_and_continue(caplog):
+    physical = PhysicalSchema(
+        database="d", schema="s", introspected_at=datetime(2026, 1, 1),
+        tables={"t": TablePhysical(columns={
+            "bad": ColumnPhysical(type="text"), "good": ColumnPhysical(type="text")
+        })},
+    )
+
+    class Dwh:
+        def sample_column(self, table, column, *, limit):
+            if column == "bad":
+                raise RuntimeError("denied")
+            return ["kept"]
+
+    _add_examples(Dwh(), physical, ExamplesConfig(max_per_column=3))
+    assert physical.tables["t"].columns["bad"].examples == []
+    assert physical.tables["t"].columns["good"].examples == ["kept"]
+    assert "Campionamento saltato" in caplog.text