Allow the symfony/runtime Composer plugin; fresh builds fail with PluginBlockedException on Drupal 11.4

Problem/Motivation

A fresh composer create-project drupal/varbase_project build on the Drupal 11.4 dependency stack fails during composer install with:

symfony/runtime contains a Composer plugin which is blocked by your allow-plugins config.

symfony/runtime arrived as a new transitive dependency of the Drupal ~11.4.0 stack, and it is not listed in config.allow-plugins in the project template's composer.json, so every fresh build aborts with PluginBlockedException. This affects both the 10.1.x and 11.0.x branches.

Steps to reproduce

composer create-project drupal/varbase_project:10.1.x-dev (or :11.0.x-dev) and let the scaffold run composer install: the install aborts with the symfony/runtime PluginBlockedException.

Proposed resolution

Add "symfony/runtime": true to config.allow-plugins in composer.json on the 10.1.x and 11.0.x branches.

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 varbase-10.1.1, varbase_project-10.1.1

User interface changes

• N/A

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• Fixed fresh project builds on Drupal 11.4: the new symfony/runtime Composer plugin is now allowed in the project template, so composer install no longer aborts with PluginBlockedException.