Prompt for overwriting operations

[Pomax]

• File rename when a same-pathed file already exists
• File drag-and-drop when a same-named file already exists at that level
• File upload when a same-named file already exists at that level
• Dir rename when a same-pathed dir already exists
• Dir drag-and-drop when a same-named dir already exists at that level
• Dir upload when a same-named dir already exists at that level

[Pomax]

Note: overwriting is fine, as long as we first get permission to do so.

[Pomax]

On further consideration, overwriting should be an error, just like in a normal shell session.