Implements checkpoint-list and checkpoint-delete CLI commands for the
plans subsystem, enabling users to view and manage checkpoints through
the command-line interface.
- Added checkpoint-list command with --sort, --type, and --format options
- Added checkpoint-delete command with batch deletion and --yes flag
- Added BDD feature file with 17 scenarios covering all acceptance criteria
- Added step definitions for all scenarios
- Updated CHANGELOG.md
ISSUES CLOSED: #8559
# Conflicts:
# CHANGELOG.md