fix(dwh): validate adapter limits strictly

harness/tht/db/sampling.py

@@ -4,6 +4,7 @@ from dataclasses import dataclass
 from sqlalchemy import Engine, text
 
 from tht.config import ExamplesConfig, LshConfig
+from tht.execute import require_positive_int
 from tht.mschema.models import Annotations, PhysicalSchema
 from tht.ports.dwh import DistinctValues
 
@@ -26,8 +27,7 @@ def _quoted_top_values_query(engine: Engine, schema: str, table: str, column: st
 def sample_column(
     engine: Engine, schema: str, table: str, column: str, *, limit: int
 ) -> list[object]:
-    if limit <= 0:
-        raise ValueError("limit must be a positive integer")
+    limit = require_positive_int(limit, name="limit")
     query = _quoted_top_values_query(engine, schema, table, column)
     with engine.connect() as conn:
         rows = conn.execute(query, {"lim": limit}).fetchall()
@@ -37,8 +37,7 @@ def sample_column(
 def sample_column_rest(
     client, schema: str, table: str, column: str, *, limit: int
 ) -> list[object]:
-    if limit <= 0:
-        raise ValueError("limit must be a positive integer")
+    limit = require_positive_int(limit, name="limit")
     rows = client.top_values(schema, table, column, limit)
     return [row["value"] for row in rows if row.get("value") is not None]
 
@@ -51,6 +50,7 @@ def distinct_values(
     *,
     max_values: int = DEFAULT_DISTINCT_VALUES_LIMIT,
 ) -> DistinctValues:
+    max_values = require_positive_int(max_values, name="max_values")
     values = sample_column(engine, schema, table, column, limit=max_values + 1)
     return DistinctValues(values=values[:max_values], truncated=len(values) > max_values)
 
@@ -63,6 +63,7 @@ def distinct_values_rest(
     *,
     max_values: int = DEFAULT_DISTINCT_VALUES_LIMIT,
 ) -> DistinctValues:
+    max_values = require_positive_int(max_values, name="max_values")
     values = sample_column_rest(client, schema, table, column, limit=max_values + 1)
     return DistinctValues(values=values[:max_values], truncated=len(values) > max_values)