#### Fixes #52579

When quickly pressing and releasing Ctrl+Tab, the tab switcher popover
would briefly appear, and any mouse movement over it would select a
random tab instead of the intended recently-focused file.

### Fix : 
This adds a 300ms delay before showing the tab switcher UI when opened
via modifier keys. If the modifier is released before the delay elapses,
the selected item is confirmed directly without ever showing the
popover. This matches the behavior of system window switchers (e.g.
macOS Cmd+Tab), where quick presses never flash the UI.

- `visible` and `_show_task` fields track whether the popover should be
rendered
- When not yet visible, the picker is mounted in a zero-size
overflow-hidden container to preserve focus and keyboard state
- When modifiers are released before the popover is visible, `confirm()`
is called directly instead of dispatching `menu::Confirm`, avoiding any
mouse-hover-based selection

### Self-Review Checklist

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments — *N/A, no unsafe
blocks*
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
— *Matches system window switcher behavior (e.g. macOS Cmd+Tab); no
visual change for slow/held switches*
- [x] Tests cover the new/changed behavior — *Added
`test_quick_switch_before_popover_visible`*
- [x] Performance impact has been considered and is acceptable — *Only
adds a lightweight 300ms timer task; no extra allocations or rendering
cost*

### Video 

[Screencast from 2026-03-29
11-52-07.webm](https://github.com/user-attachments/assets/8e148a74-75ae-4c36-8d44-594c3c9097e6)



### Note : Reopens previous work from closed PR #52648 (fork was deleted
by mistake)


Release Notes:

- Fixed Ctrl+Tab jumping to random documents when the mouse is moved
during a quick tab switch

---------

Co-authored-by: Piotr Osiewicz <24362066+osiewicz@users.noreply.github.com>