Switch the default ECA modeler from BPMN.iO to the Workflow Modeler

Problem/Motivation

Varbase Content Base enables the BPMN.iO modeler (bpmn_io) as the visual editor for ECA (Modeler API) models, including the two ECA models this recipe ships: "Activate Full content view mode for new node types" and "Redirect 403 to Login".

Workflow Modeler (drupal/modeler) is a newer, React-Flow-based editor for the same Modeler API models. It adds live execution replay ("Review flow") and opens all existing BPMN.iO-authored models with no migration: the model itself is stored as the eca.eca.* config entity, the editor only re-derives the diagram from it.

This recipe should ship the Workflow Modeler as the default editor going forward.

Steps to reproduce

1. Install the Varbase Content Base recipe.
2. Go to Admin > Configuration > Workflow > ECA (/admin/config/workflow/eca) and edit either shipped model.
3. Note the model opens in the BPMN.iO editor, because recipe.yml enables bpmn_io and both models are tagged modeler_id: bpmn_io.

Proposed resolution

• Enable modeler instead of bpmn_io in recipe.yml.
• Require drupal/modeler (~1.0) instead of drupal/bpmn_io (~3) in composer.json.
• Retag the two shipped ECA models (eca.eca.enable_full_view_mode_node_type.yml and eca.eca.redirect_403_to_login.yml) to modeler_id: workflow_modeler, and stop shipping the BPMN.iO raw diagram data (drop the data: 'hash:...' line and the config/modeler_api.data_model.eca_bpmn_io_redirect_403_to_login.yml BPMN 2.0 XML file, no longer needed once the editor re-derives the diagram from the config entity).
• bpmn_io stays available as a transitive dependency of eca for sites that still want it, but is no longer enabled by this recipe.

This issue, and the patch attached to its merge request, were created with AI assistance (Claude Code), per the Drupal policy on the use of AI when contributing to Drupal.

Remaining tasks

• ✅ File an issue about this project
• ❌ Addition/Change/Update/Fix to this project
• ❌ Testing to ensure no regression
• ➖ Automated unit/functional testing coverage
• ➖ Developer Documentation support on feature change/addition
• ➖ User Guide Documentation support on feature change/addition
• ➖ UX/UI designer responsibilities
• ➖ Accessibility and Readability
• ❌ Reviewed by a human
• ❌ Code review by maintainers
• ❌ Full testing and approval
• ❌ Credit contributors
• ❌ Review with the product owner
• ❌ Update Release Notes
• ❌ Release

User interface changes

• The ECA model edit form now opens in the Workflow Modeler (React Flow based) instead of BPMN.iO.

API changes

• N/A

Data model changes

• The two shipped eca.eca.* config entities change their third_party_settings.modeler_api.modeler_id from bpmn_io to workflow_modeler; the BPMN.iO raw diagram data (data: 'hash:...' property and the companion modeler_api.data_model.eca_bpmn_io_redirect_403_to_login config object) is removed as it is no longer used.

Release notes snippet

• The Varbase Content Base recipe now ships the Workflow Modeler as the default ECA editor instead of BPMN.iO.