Trim and validate scene caveats

internal/modules/chunk/dnd/scenes/chunker_test.go

@@ -94,7 +94,7 @@ func TestChunkReturnsSceneChunksFromStructuredOutput(t *testing.T) {
 					BoundaryConfidence: "Medium",
 				},
 			},
-			BoundaryCaveats: []string{"The transition into combat is gradual."},
+			BoundaryCaveats: []string{" The transition into combat is gradual. "},
 		},
 	}
 
@@ -162,6 +162,25 @@ func TestChunkReturnsSceneChunksFromStructuredOutput(t *testing.T) {
 	}
 }
 
+func TestChunkRejectsWhitespaceOnlyBoundaryCaveats(t *testing.T) {
+	client := &fakeScenesLLMClient{
+		response: chunkResponse{
+			Scenes: validSceneResponse().Scenes,
+			BoundaryCaveats: []string{
+				"   ",
+			},
+		},
+	}
+
+	_, err := New().Chunk(context.Background(), chunkRequestWithClient(client))
+	if err == nil {
+		t.Fatal("Chunk() error = nil, want malformed structured output error")
+	}
+	if !strings.Contains(err.Error(), "dnd scenes chunker") || !strings.Contains(err.Error(), "malformed structured output") || !strings.Contains(err.Error(), "boundary_caveats[0]") {
+		t.Fatalf("Chunk() error = %q, want malformed boundary caveat context", err.Error())
+	}
+}
+
 func TestChunkDefensivelyCopiesSourceUnitsAndMetadata(t *testing.T) {
 	doc := sceneSourceDocument()
 	client := &fakeScenesLLMClient{response: validSceneResponse()}