revisit file hierarchy selection ux

[ngwese]

the current file tree selection mechanism could benefit from a rethink. there are effectively two selections the ui is tracking - (a) the file currently being edited in the buffer and (b) the last directory selected. the selection indicators are rather faint and the dual selection behavior is unusual.

things to consider:

• make the selection indicator be a background strip which runs the width of the tree view (typical in file browsers)
• file rename continues to be confusing and/or buggy. investigate editing of the name directly in the tree view instead of a pop up dialog
• increase contrast overall

Reference: https://llllllll.co/t/norns-maiden/14052/120