fix(types): consolidate enhancement alias and fix update command

- Add "enhancement" to util.issueTypeAliases for consistency
- Make types.IssueType.Normalize() case-insensitive and include all aliases
- Fix update.go to normalize type before validation
- Remove duplicate type validation block in update.go

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cmd/bd/update.go

@@ -12,6 +12,7 @@ import (
 	"github.com/steveyegge/beads/internal/timeparsing"
 	"github.com/steveyegge/beads/internal/types"
 	"github.com/steveyegge/beads/internal/ui"
+	"github.com/steveyegge/beads/internal/util"
 	"github.com/steveyegge/beads/internal/validation"
 )
 
@@ -103,7 +104,8 @@ create, update, show, or close operation).`,
 		}
 		if cmd.Flags().Changed("type") {
 			issueType, _ := cmd.Flags().GetString("type")
-			// Validate issue type
+			// Normalize aliases (e.g., "enhancement" -> "feature") before validating
+			issueType = util.NormalizeIssueType(issueType)
 			if !types.IssueType(issueType).IsValid() {
 				FatalErrorRespectJSON("invalid issue type %q. Valid types: bug, feature, task, epic, chore, merge-request, molecule, gate, agent, role, rig, convoy, event, slot", issueType)
 			}
@@ -125,14 +127,6 @@ create, update, show, or close operation).`,
 			parent, _ := cmd.Flags().GetString("parent")
 			updates["parent"] = parent
 		}
-		if cmd.Flags().Changed("type") {
-			issueType, _ := cmd.Flags().GetString("type")
-			// Validate issue type
-			if _, err := validation.ParseIssueType(issueType); err != nil {
-				FatalErrorRespectJSON("%v", err)
-			}
-			updates["issue_type"] = issueType
-		}
 		// Gate fields (bd-z6kw)
 		if cmd.Flags().Changed("await-id") {
 			awaitID, _ := cmd.Flags().GetString("await-id")