Add extract worker configuration controls

internal/core/config/validation_test.go

@@ -79,6 +79,41 @@ func TestValidateRejectsInvalidNumericFields(t *testing.T) {
 	}
 }
 
+func TestValidateStageWorkerBoundaries(t *testing.T) {
+	for _, test := range []struct {
+		name    string
+		workers int
+		wantErr bool
+	}{
+		{name: "below minimum", workers: 0, wantErr: true},
+		{name: "minimum", workers: 1},
+		{name: "maximum", workers: 4},
+		{name: "above maximum", workers: 5, wantErr: true},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			cfg := validConfig()
+			cfg.Concurrency.TotalLLM = 4
+			cfg.Concurrency.StageWorkers["extract"] = test.workers
+			err := cfg.Validate()
+			if test.wantErr && (err == nil || !strings.Contains(err.Error(), "stage_workers.extract")) {
+				t.Fatalf("Validate() error = %v, want extract worker range error", err)
+			}
+			if !test.wantErr && err != nil {
+				t.Fatalf("Validate() error = %v, want nil", err)
+			}
+		})
+	}
+}
+
+func TestValidateRejectsUnknownEffectiveStageWorkerKey(t *testing.T) {
+	cfg := validConfig()
+	cfg.Concurrency.StageWorkers["merge"] = 1
+	err := cfg.Validate()
+	if err == nil || !strings.Contains(err.Error(), "stage_workers key") || !strings.Contains(err.Error(), "merge") {
+		t.Fatalf("Validate() error = %v, want unknown stage worker key", err)
+	}
+}
+
 func TestValidateRejectsMutuallyExclusiveScriptoriumProfileSources(t *testing.T) {
 	cfg := validConfig()
 	cfg.Scriptorium.ProfileDir = "./profiles"