refactor(output): share the JSON, created-resource and batch tails

Mutations end with a.jsonResult or a.created instead of hand-rolled
--json branches, the two identical jsonResult/writeMutationJSON helpers
become one, and writeBatchJSON checks --json itself so batch commands
share one tail.

Signed-off-by: bircni <bircni@icloud.com>

internal/app/metadata.go

@@ -274,11 +274,8 @@ $ tea milestone create --title v2.0 --editor`, Args: usageArgs(cobra.MaximumNArg
 		if err != nil {
 			return err
 		}
-		if a.options.json != "" {
-			return a.writeJSON(cmd, item)
-		}
 		a.done(cmd, "Created %s", milestoneName(t, item))
-		return a.printURL(cmd, milestoneURL(t, item))
+		return a.created(cmd, item, milestoneURL(t, item))
 	}}
 	fields.register(cmd)
 	enumFlag(cmd, &state, "state", "", "open", "State of the new milestone", "open", "closed")
@@ -338,11 +335,8 @@ $ tea milestone edit 3 --editor`, Annotations: map[string]string{"tea.arguments"
 		if err != nil {
 			return err
 		}
-		if a.options.json != "" {
-			return a.writeJSON(cmd, item)
-		}
 		a.done(cmd, "Edited %s", milestoneName(t, item))
-		return nil
+		return a.jsonResult(cmd, item)
 	}}
 	fields.register(cmd)
 	cmd.Flags().BoolVar(&byName, "by-name", false, "Match a numeric argument as a milestone title rather than an ID")
@@ -369,11 +363,8 @@ $ tea milestone delete 7 --yes`, Annotations: map[string]string{"tea.confirm": "
 		if err := s.Delete(cmd.Context(), item.ID); err != nil {
 			return err
 		}
-		if a.options.json != "" {
-			return a.writeJSON(cmd, item)
-		}
 		a.done(cmd, "Deleted milestone %q from %s", item.Title, t.Repo)
-		return nil
+		return a.jsonResult(cmd, item)
 	}}
 	cmd.Flags().BoolVar(&byName, "by-name", false, "Match a numeric argument as a milestone title rather than an ID")
 	cmd.ValidArgsFunction = a.completeMilestoneArgs(false)