Make chunk validation a framework contract

internal/framework/contracts/contracts_test.go

@@ -117,6 +117,27 @@ func TestFakeChunkerReturnsSourceChunks(t *testing.T) {
 	}
 }
 
+func TestFakeChunkerReceivesLLMClient(t *testing.T) {
+	doc := &source.SourceDocument{
+		ID:     "source-1",
+		Kind:   "document",
+		Format: "text/plain",
+		Digest: "sha256:abc123",
+		Units: []source.SourceUnit{
+			{ID: "u1", Kind: "section", Text: "Source text."},
+		},
+	}
+	client := fakeLLMClient{}
+	chunker := &recordingChunker{key: "llm-chunker"}
+
+	if _, err := chunker.Chunk(context.Background(), ChunkRequest{Source: doc, LLMClient: client}); err != nil {
+		t.Fatalf("Chunk() error = %v, want nil", err)
+	}
+	if chunker.request.LLMClient == nil {
+		t.Fatal("ChunkRequest.LLMClient = nil, want structured LLM client")
+	}
+}
+
 func TestFakeExtractorReceivesChunkAndAmbientContext(t *testing.T) {
 	extractor := fakeExtractor{
 		key:           "generic-extractor",
@@ -305,6 +326,20 @@ func (chunker fakeChunker) Chunk(ctx context.Context, req ChunkRequest) (ChunkRe
 	}, nil
 }
 
+type recordingChunker struct {
+	key     string
+	request ChunkRequest
+}
+
+func (chunker *recordingChunker) Key() string {
+	return chunker.key
+}
+
+func (chunker *recordingChunker) Chunk(ctx context.Context, req ChunkRequest) (ChunkResult, error) {
+	chunker.request = req
+	return fakeChunker{key: chunker.key}.Chunk(ctx, req)
+}
+
 type fakeExtractor struct {
 	key           string
 	artifactType  string