[Feature]: Option to position the terminal tab bar at the bottom

### Problem or use case

In an agentic-coding app, attention lives at the bottom of the window — the agent/terminal input box is there. But the tab bar is fixed at the top, so every tab switch means moving the mouse (and eyes) all the way up and back down. That round trip is inefficient for the core workflow of driving multiple agents in parallel.

I wanted this badly enough that I built a patch myself and use it daily: https://gitlab.com/spiegel/orca-bottom-tabs — it rewrites the CSS inside the installed app.asar to flip the tab strip to the bottom (the drag region moves with it). It works, but it breaks on every Orca update, so I also had to build a launcher that re-applies it on start.

### Proposed solution

A built-in appearance setting to choose the tab bar position, e.g. `tabBar.position: top | bottom`, so this doesn't require binary patching.

### Alternatives or additional context

_No response_