feat: reclaim 'cog run' for predictions, deprecate 'cog predict'
- Create new 'cog run' command that runs predictions (replaces 'cog predict')
- 'cog predict' is hidden and prints deprecation warning
- 'cog run <cmd> [args...]' (2+ args) forwards to 'cog exec' with deprecation warning
- Remove 'run' alias from exec command
