Feat v0.9.6 deprecate stage_type, collapse stage_mode

stage_type no longer validated — starlark_hook presence determines
automation. stage_mode collapsed from 4→3 values (form/delegated/
automated); "review" mapped to "form" on input for backward compat.
Migration 018 converts existing rows. Review surface removed (~110
lines). 4 package manifests updated.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/handlers/workflow_packages.go

@@ -55,7 +55,6 @@ func (h *WorkflowPackageHandler) ExportWorkflowPackage(c *gin.Context) {
 			"ordinal":         s.Ordinal,
 			"stage_mode":      s.StageMode,
 			"audience":        s.Audience,
-			"stage_type":      s.StageType,
 			"auto_transition": s.AutoTransition,
 		}
 		if s.AssignmentTeamID != nil {
@@ -230,6 +229,7 @@ func InstallWorkflowFromManifest(ctx *gin.Context, stores store.Stores, pkgID st
 			StarlarkHook:     s.StarlarkHook,
 			SLASeconds:       s.SLASeconds,
 		}
+		st.StageMode = models.NormalizeStageModeInput(st.StageMode)
 		if st.StageMode == "" {
 			st.StageMode = models.StageModeDelegated
 		}
@@ -284,7 +284,7 @@ type workflowPkgStage struct {
 	Ordinal          int     `json:"ordinal"`
 	StageMode        string  `json:"stage_mode"`
 	Audience         string  `json:"audience"`
-	StageType        string  `json:"stage_type"`
+	StageType        string  `json:"stage_type"` // deprecated — kept for backward-compat deserialization
 	AutoTransition   bool    `json:"auto_transition"`
 	AssignmentTeamID *string `json:"assignment_team_id,omitempty"`
 	SurfacePkgID     *string `json:"surface_pkg_id,omitempty"`