Implement resume, skip, and stage selection

internal/app/runner.go

@@ -29,6 +29,8 @@ type RunSummary struct {
 	SessionID    string
 	ManifestPath string
 	StageNames   []string
+	Executed     []string
+	Skipped      []string
 }
 
 func executeStages(ctx context.Context, cfg *config.Config, stages []stage.Stage, opts RunOptions) (*RunSummary, error) {
@@ -89,12 +91,21 @@ func executeStages(ctx context.Context, cfg *config.Config, stages []stage.Stage
 
 	stageEnv := toStageEnv(env)
 
-	_ = opts.Force // TODO: use --force behavior in future skip/stale logic.
+	decisions := decideStageActions(stages, m, opts.Force)
 
-	runNames := make([]string, 0, len(stages))
-	for _, s := range stages {
+	runNames := make([]string, 0, len(decisions))
+	executed := make([]string, 0, len(decisions))
+	skipped := make([]string, 0, len(decisions))
+	for _, d := range decisions {
+		s := d.Stage
 		runNames = append(runNames, s.Name())
 
+		if d.Action == stageActionSkip {
+			skipped = append(skipped, s.Name())
+			continue
+		}
+		executed = append(executed, s.Name())
+
 		now := nowUTC()
 		m.MarkStageRunning(s.Name(), now)
 		if err := env.ManifestStore.Save(ctx, manifestPath, m); err != nil {
@@ -123,6 +134,8 @@ func executeStages(ctx context.Context, cfg *config.Config, stages []stage.Stage
 		SessionID:    cfg.Session.SessionID,
 		ManifestPath: manifestPath,
 		StageNames:   runNames,
+		Executed:     executed,
+		Skipped:      skipped,
 	}, nil
 }