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/pull_create.go

@@ -371,8 +371,5 @@ func (a *application) createPullInteractively(cmd *cobra.Command, snapshot setti
 // reportCreatedPull reports a new pull request and prints its URL, or the pull request as JSON.
 func (a *application) reportCreatedPull(cmd *cobra.Command, t target, item services.Pull) error {
 	a.done(cmd, "Created pull request %s", refLabel(t.Repo, item.Number, item.Title))
-	if a.options.json != "" {
-		return a.writeJSON(cmd, item)
-	}
-	return a.printURL(cmd, item.URL)
+	return a.created(cmd, item, item.URL)
 }