Update pipeline defaults so trim is enabled when omitted

internal/stage/trim.go

@@ -71,7 +71,7 @@ func (trimStage) Run(ctx context.Context, env *Env, m *manifest.Manifest) (*Stag
 	}
 
 	trimCfg := env.Config.Pipeline.Trim
-	enabled := trimCfg != nil && trimCfg.Enabled
+	enabled := trimCfg != nil && trimCfg.Enabled != nil && *trimCfg.Enabled
 
 	canonicalTrimmedPath, err := resolveTrimmedOutputPath(paths, trimCfg)
 	if err != nil {

internal/stage/trim_test.go

@@ -275,7 +275,8 @@ func TestTrimStageDisabledCopiesNormalizedTranscript(t *testing.T) {
 	writeFile(t, normalized, normalizedBody)
 
 	disabled := *env.Config.Pipeline.Trim
-	disabled.Enabled = false
+	enabled := false
+	disabled.Enabled = &enabled
 	env.Config.Pipeline.Trim = &disabled
 
 	result, err := (trimStage{}).Run(context.Background(), env, m)
@@ -424,6 +425,7 @@ func setupTrimEnv(t *testing.T) (*Env, *manifest.Manifest, *boundsScriptoriumRun
 	writeFile(t, pipelinePath, "workspace:\n  root: "+workspace+"\n")
 
 	seriatimReport := false
+	trimEnabled := true
 	cfg := &config.Config{
 		PipelinePath: pipelinePath,
 		SessionPath:  sessionPath,
@@ -437,7 +439,7 @@ func setupTrimEnv(t *testing.T) (*Env, *manifest.Manifest, *boundsScriptoriumRun
 				Report:       &seriatimReport,
 			},
 			Trim: &config.TrimConfig{
-				Enabled:    true,
+				Enabled:    &trimEnabled,
 				OutputPath: "transcripts/final.trimmed.json",
 				Bounds: config.TrimBoundsConfig{
 					PromptID:            "dnd_session.bounds",