text: Title: [UX] Sky silently treat task YAML as command when there is an extra space
  Body: ## Repro
  
  ```
  $ sky launch task.yaml -c test --env A= c
  Command to run: task.yaml c
  
  $  sky launch task.yaml -c test --env A=c
  YAML to run: task.yaml
  ```
  
  `sky launch` collects all args without an option key as entrypoint, which is counter-intuitive and hides typo error like above