Create Omni/Jr.hs (Main entry point)

Create the main entry point for the new 'jr' CLI (Omni/Jr.hs). This module should handle command-line argument parsing (using docopt) and dispatch to sub-commands. The main function should delegate to a Cli.main style handler. Reference Plan: /home/ben/omni/_/llm/PLAN_Jr_Evolution.md. Acceptance Criteria: Omni/Jr.hs module exists, jr --help prints usage info, supports subcommands: task, work, harvest, and main function delegates correctly.