Webhook triggered builds are suppressed by INDEXING strategy for new repos

### Jenkins and plugins versions report

Environment

```text
Latest Jenkins LTS and plugins
```

### What Operating System are you using (both controller, and any agents involved in the problem)?

RHEL

### Reproduction steps

1. Configure an Organization Folder hosted on GitHub
2. Configure the folder with "Suppress automatic SCM triggering" using the strategy:
- **For matching branches suppress builds triggered by indexing (_continue to honor webhooks_)** / `SuppressionStrategy.INDEXING`
3. Ensure the GitHub webhook is configured and accepted by Jenkins
4. Create a new repository under the organization
5. Push a `Jenkinsfile` to a matching branch so the webhook triggers repository/branch discovery
6. Wait for the webhook-triggered organization folder scan/multibranch computation to finish
7. Check the newly created branch job and build history

### Expected Results

When the suppression strategy is `INDEXING`, builds caused by ordinary indexing (periodic scans or manual scans via UI) should be suppressed, but webhook triggered builds should still be allowed.

If a webhook causes Jenkins to discover a new repository or branch, Jenkins should create the branch job and schedule the first build automatically.

### Actual Results

The webhook is received and the organization folder/multibranch computation runs, but the first build for the newly discovered branch is not scheduled.

The branch job is created, but the build is suppressed as if it came from plain branch indexing. Manually triggering the build works, and disabling the suppression strategy also allows the build to run.

### Anything else?

_No response_

### Are you interested in contributing a fix?

Yes. I have opened https://github.com/jenkinsci/branch-api-plugin/pull/818