Add BackupTool for creating, listing, verifying, and restoring
timestamped workspace backups with SHA-256 manifest integrity
checking. Add DataManagementTool for retention status, time-based
purge, and storage statistics. Both tools are config-driven via
new BackupConfig and DataRetentionConfig sections.
Original work by @rareba. Rebased on latest master with conflict
resolution for SwarmConfig/SwarmStrategy exports and swarm tool
registration, and added missing approval_manager fields in
ChannelRuntimeContext test constructors.
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
