Forgejo editorial workflow - creating a new post fails

**Describe the bug**
When attempting to use the new editorial workflow support for Forgejo, creating a new post results in failures after saving. The editorial branch is created but then it doesn't show up in the workflow pane and `content is not under editorial workflow` errors flood in.

**To Reproduce**
1. In existing Hugo repository on Forgejo with DecapCMS installed and working, change `publish_mode` to `editorial_workflow`.
2. Create a new post.
3. Reload page.
4. Observe `content is not under editorial workflow` errors

**Expected behavior**
Post should be created and available to edit in workflow pane.

**Screenshots**
N/A

**Applicable Versions:**
- Decap CMS version: 3.15.1
- Git provider: Forgejo 16.0.1
- OS: Mac OS
- Browser version: Safari 26.6

**CMS configuration**

```yaml
backend:
name: forgejo
repo: [redacted]
app_id: [redacted]
api_root: [redacted]
base_url: [redacted]
auth_endpoint: [redacted]
branch: editorial

publish_mode: editorial_workflow
media_folder: static/images
public_folder: /images
collections:
- name: 'posts'
label: 'Posts'
label_singular: 'Post'
folder: 'content/posts'
preview_path: 'posts/{{slug}}'
create: true
path: '{{slug}}/index'
media_folder: ''
public_folder: ''
editor:
preview: false
fields:
- { label: 'Title', name: 'title', widget: 'string' }
- { label: 'Publish Date', name: 'date', widget: 'datetime' }
- { label: 'Categories', name: 'categories', widget: 'list' }
- { label: 'Featured image', name: 'image', widget: 'image' }
- label: 'Gallery Images'
name: 'gallery_images'
widget: 'list'
field: {label: Image, name: image, widget: image}
- { label: 'Body', name: 'body', widget: 'markdown' }
```

Reproduce the failure in an existing Hugo repository using the supplied Forgejo configuration and Decap CMS 3.15.1, then trace the editorial workflow handling around the “content is not under editorial workflow” error. Done means a newly created post appears in the workflow pane and can be edited without repeated errors.

Written by the indexing model from the issue text.