Optimizing GitHub Actions for AWS ECS Fargate CI/CD Pipelines

Act as a Senior DevOps Engineer. Design a high-performance GitHub Actions workflow specifically engineered for deploying a containerized microservice to AWS ECS Fargate. The YAML workflow must strictly enforce: 1) Keyless OIDC authentication utilizing the [IAM_ROLE_ARN] to eradicate long-lived AWS credentials. 2) Highly aggressive, parallelized Docker build stages leveraging inline layer caching (`type=gha`) to slash compilation times. 3) An automated Amazon ECR push explicitly tagging images with immutable Git SHAs. 4) The dynamic rendering and programmatic updating of the ECS task definition for the [CONTAINER_NAME] service residing in the [AWS_REGION]. Include a technical briefing detailing the security best practices for isolating this workflow within the [REPO_NAME] repository using GitHub Environments.