Isolate invocation collaborator composition

internal/app/runner_test.go

@@ -71,6 +71,59 @@ func TestExecutePlanPreservesSessionLockReleaseErrors(t *testing.T) {
 	}
 }
 
+func TestExecutePlanUsesInvocationClockAndRunID(t *testing.T) {
+	cfg := testConfig(t)
+	fixed := time.Date(2026, time.September, 4, 1, 2, 3, 0, time.UTC)
+	runID := "20260904T010203Z-a1b2c3d4"
+	summary, err := executePlanWithDependencies(
+		context.Background(),
+		cfg,
+		BoundedPlan{stages: []stage.Stage{resultStage{name: "prepare"}}},
+		RunOptions{},
+		invocationDependencies{
+			now:      func() time.Time { return fixed },
+			newRunID: func() (string, error) { return runID, nil },
+		},
+	)
+	if err != nil {
+		t.Fatalf("executePlanWithDependencies() error = %v", err)
+	}
+	if summary.RunID != runID {
+		t.Fatalf("summary run id = %q, want %q", summary.RunID, runID)
+	}
+	persisted, err := (&manifest.LocalStore{}).Load(context.Background(), summary.ManifestPath)
+	if err != nil {
+		t.Fatalf("load manifest: %v", err)
+	}
+	record := persisted.Stages["prepare"]
+	if record == nil || record.StartedAt == nil || !record.StartedAt.Equal(fixed) || record.CompletedAt == nil || !record.CompletedAt.Equal(fixed) {
+		t.Fatalf("prepare timestamps = %#v, want invocation clock %v", record, fixed)
+	}
+}
+
+func TestExecutePlanDoesNotConstructUnselectedObjectStore(t *testing.T) {
+	cfg := testConfig(t)
+	constructed := false
+	_, err := executePlanWithDependencies(
+		context.Background(),
+		cfg,
+		BoundedPlan{stages: []stage.Stage{resultStage{name: "prepare"}}},
+		RunOptions{},
+		invocationDependencies{
+			newObjectStore: func(context.Context, *config.Config) (storage.ObjectStore, error) {
+				constructed = true
+				return nil, errors.New("must not construct object store")
+			},
+		},
+	)
+	if err != nil {
+		t.Fatalf("executePlanWithDependencies() error = %v", err)
+	}
+	if constructed {
+		t.Fatal("object store was constructed for an invocation that does not require it")
+	}
+}
+
 type countingStage struct {
 	name string
 	runs *int