Ctrl-Tab and Ctrl-Shift-Tab have incorrect behavior

[phated]

As per #88 (comment)

Ctrl-Tab and Ctrl-Shift-Tab
As implemented in v0.3.0, it's not exactly what I indended. The intent was to provide navigation to the next or previous file recently opened. In other words, imagine the app is a multi-tabbed browser, but without the tabs. But even without tabs, the Ctrl-Tab and Ctrl-Shift-Tab combinations switch the edit view to the next or previous source that is opened.

[PropGit]

To follow-up, this implies that there's an internally-kept list of source that is known to be "opened" due to user interactions, and Ctrl-Tab and Ctrl-Shift-Tab quickly switches between them (forward or backward, respectfully). In other words, those key combinations do not simply open the next or previous file that appears in the Project View.