TODO: Add an up-to-date walkthrough of undo/redo, editing command history, and saving or replaying the resulting commands as a Docfd script.
TODO: Describe the command representation, session state, committed versus preview commands, and how snapshots connect commands to states.
TODO: Explain why retaining every snapshot state consumed too much memory, which states are retained, and when compaction occurs.
TODO: Explain how a missing snapshot is reconstructed from the nearest preceding checkpoint by replaying commands.
TODO: Cover history truncation after editing an older version, input-field synchronization, worker quiescence, and the blocking reconstruction overlay.
TODO: Discuss the memory-versus-reconstruction-time trade-off and whether timing command replay could support better checkpoint heuristics.