Phase 13: Build CLI commands for headless and automation use #14

Goal

Make Magicloder useful without the desktop UI.

Scope

• Add commands such as add, list, info, pause, resume, cancel, remove, retry, and serve.
• Support JSON output for scripts.
• Add readable table output for humans.
• Use the local API rather than duplicating engine logic.
• Return meaningful exit codes.
• Support stdin/file input for batches of URLs.

Acceptance criteria

• Every lifecycle action available in the UI is available through CLI/API.
• CLI never directly manipulates SQLite internals.
• Commands have shell-friendly exit codes and tests.