Automatically execute commands instead of selecting the type of command manually

Currently, the users have to select which type of command they are entering before pressing the `Run` button. Most of the compilers do not ask for such input and directly run the command(s).

Start by tracing the command-type selection and the Run button flow in the browser-based SQL compiler. Determine how commands are currently classified before execution, then make completion mean that users can press Run without manually selecting a command type. Verify the existing compiler flows still execute correctly.

Written by the indexing model from the issue text.