Closes#76
Session history was recorded only after receiving `IRIS_CMD_STOP`.
Directly launched Bash sessions may not install that completion hook,
and Bash does not flush `.bash_history` until the shell exits.
There was also a race where `Enter` was sent to the shell before Iris
stored the submitted command, allowing fast commands to finish before
the command was captured.
The fix is
- Record commands in session history immediately when they are
submitted.
- Store the submitted command before sending Enter to the shell.
- Keep command-completion handling responsible for exit-code and
frecency data.
Once again (and please tell me if you prefer not) I'm not fluent in `go`
so this was all Sol
Paolo Ricciuti