docs: document S3-native state locking (useLockfile) for the S3 backend#17

so0k merged 2 commits into

mainopen-constructs/cdk-terrain-docs:mainfrom

claude/s3-backend-locking-docs-6ethbeopen-constructs/cdk-terrain-docs:claude/s3-backend-locking-docs-6ethbeCopy head branch name to clipboard