Creating a Backstage Scaffolder Action

Use when building a custom scaffolder template action — a step that scaffolder templates can call from their YAML steps. Covers createTemplateAction with Zod input/output schemas, the action handler context (logger, workspacePath, input, output, etc.), and module wiring via scaffolderActionsExtensionPoint. Triggers on phrases like "scaffolder action", "template action", "custom action".