Add remote session loading

internal/stage/prepare.go

@@ -113,6 +113,23 @@ func (prepareStage) Run(ctx context.Context, env *Env, m *manifest.Manifest) (*S
 	registerConfigInput := func(kind, path, checksum, source string) {
 		inputs = append(inputs, manifest.InputRecord{Kind: kind, Path: path, Checksum: checksum, Source: source})
 	}
+	registerSessionConfigInput := func(path, checksum string) {
+		source := env.Config.SessionSource
+		if strings.TrimSpace(source.Source) == "" {
+			source.Source = "session_config"
+		}
+		inputs = append(inputs, manifest.InputRecord{
+			Kind:      "session_config",
+			Path:      path,
+			Checksum:  checksum,
+			Source:    source.Source,
+			S3Bucket:  source.S3Bucket,
+			S3Key:     source.S3Key,
+			S3Size:    source.S3Size,
+			S3ETag:    source.S3ETag,
+			SpoolPath: source.SpoolPath,
+		})
+	}
 
 	campaignDst := filepath.Join(paths.InputsDir, "campaign.yml")
 	campaignChecksum, err := copyFileIfChanged(env.ArtifactStore, campaignSrc, campaignDst)
@@ -126,7 +143,7 @@ func (prepareStage) Run(ctx context.Context, env *Env, m *manifest.Manifest) (*S
 	if err != nil {
 		return nil, fmt.Errorf("prepare: materialize session.yml: %w", err)
 	}
-	registerConfigInput("session_config", sessionDst, sessionChecksum, "session_config")
+	registerSessionConfigInput(sessionDst, sessionChecksum)
 
 	pipelineResolvedBytes, err := renderResolvedPipeline(env.Config.Pipeline)
 	if err != nil {