Add fail-closed sample filters to label QA

tests/test_render_operator_yolo_label_qa_contact_sheets.py

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+import pytest
+
+from scripts.render_operator_yolo_label_qa_contact_sheets import filter_tiles_by_samples
+
+
+TILES = [
+    {"sample_slug": "genk-industry-train"},
+    {"sample_slug": "lokeren-ribbon-train"},
+    {"sample_slug": "ostend-coastal-train"},
+]
+
+
+def test_filter_tiles_by_samples_keeps_only_explicit_samples() -> None:
+    assert filter_tiles_by_samples(TILES, ["genk-industry-train", "ostend-coastal-train"]) == [
+        TILES[0],
+        TILES[2],
+    ]
+
+
+def test_filter_tiles_by_samples_rejects_missing_sample() -> None:
+    with pytest.raises(ValueError, match="absent from summary"):
+        filter_tiles_by_samples(TILES, ["missing"])
+
+
+def test_filter_tiles_by_samples_without_filter_preserves_tiles() -> None:
+    assert filter_tiles_by_samples(TILES, []) is TILES