[Bug] `Primitive` node is not saved in api format

### Prerequisites

- [x] I am running the latest version of ComfyUI
- [x] I have searched existing issues to make sure this isn't a duplicate
- [ ] I have tested with all custom nodes disabled ([see how](https://docs.comfy.org/troubleshooting/custom-node-issues#step-1%3A-test-with-all-custom-nodes-disabled))

### What happened?

Node `Primitive` (not specific Int, Float etc, but the general one that automatically decides what type is it) is not saved in API format

### Steps to Reproduce

1. Use `Primitive` node in workflow
2. File > Export (API)
3. Open this exported workflow - there is no longer this node

### How is this affecting you?

Feature doesn't work as expected

### ComfyUI Frontend Version

1.28.7

### Browser

Firefox

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-6225-Bug-Primitive-node-is-not-saved-in-api-format-2956d73d3650816195bde7f6c923f0f6) by [Unito](https://www.unito.io)