Mobile Action Bar UX

**Is your feature request related to a problem? Please describe.**
Yes. On touch devices (mobile, tablet), the radial menu has no hover state, meaning players cannot see unit descriptions or gold costs before tapping them.

**Describe the solution you'd like**
Implement a touch-friendly metadata display and action workflow on touch/mobile:
1. Touch Info Panel: A fixed-position panel pinned to the bottom-center of the screen that renders the item title, description, and gold cost.
2. Press-to-Preview: Displays this metadata on `touchstart` when holding down on a menu button.
3. Slide-to-Cancel: Tracks finger movement on `touchmove`. If the finger slides off the button, the preview disappears and the action is cancelled.
4. Action-on-Release: Tapping/releasing (`touchend`) fires the action only if the finger is still on the button.
5. Suppress Desktop Tooltip: Do not show the mouse-position-based tooltip during touch events.

**Describe alternatives you've considered**
- Showing tooltips directly under the finger (this is bad because the finger covers the text).

**Additional context**
n/a
**Assignment**

- [x] I'd like to be assigned to this issue and work on it myself

**EX:**