Add new CLI commands and subcommands: - Sessions command with list and latest subcommands for viewing session records and handoff notes - Graph command with export/import/diff subcommands for TOML interchange - Export action to Decisions command for ADR markdown file generation Implement CLI handlers that: - Open database and create appropriate stores (SessionStore, SqliteGraphStore) - Call underlying functions (export_adrs, export_goal, import_goal, diff_goal) - Format and display results appropriately - Support both stdout output and file output where applicable Verifies P1c.AC5.1-5.4 with help text validation.