CmdPal: Support double-tapping modifier keys (e.g., Ctrl, Alt) for activation

### Description of the new feature / enhancement

### Is your feature request related to a problem? Please describe.
Currently, the default activation shortcut for CmdPal is a combination of keys (e.g., `Alt+Space`). While effective, these combinations often require two hands or a specific hand position.

Many users are accustomed to "Double-Tap" activation methods found in other productivity tools (like Alfred on macOS, Listary, or Wox), where double-pressing a single modifier key (like `Left Ctrl` or `Alt`) instantly summons the launcher.

Referencing older discussion in PowerToys Run #3957, this feature is highly requested for improved accessibility and speed.

### Describe the solution you'd like
I would like to suggest adding a configuration option in the **CmdPal** settings to enable "Double-Tap to Activate".

**Proposed Settings:**
1. **Enable/Disable Toggle:** A checkbox to turn this feature on.
2. **Key Selection:** A dropdown menu to select which key to double-tap. Options should ideally include:
- Left Control
- Right Control
- Left Alt
- Right Alt
- Left Shift
3. **Sensitivity (Optional):** Adjustable timeout for what counts as a "double press" (similar to Windows mouse double-click speed).

### Describe alternatives you've considered
- Using third-party remapping tools (like AutoHotkey) to map `Double Ctrl` to the CmdPal shortcut. However, having this native to PowerToys would be much cleaner and more stable.
- Sticking to `Alt+Space`, which is less ergonomic for one-handed use compared to double-tapping a corner key like `Ctrl`.

### Additional context
**Crucially, this interaction logic is already implemented in PowerToys "Find My Mouse" utility.** The [Find My Mouse](https://learn.microsoft.com/en-us/windows/powertoys/mouse-utilities#find-my-mouse) tool successfully uses a double-press of the `Left Ctrl` key to activate the spotlight effect.
- Bringing this same functionality to **CmdPal** would maintain consistency across the PowerToys suite.
- The existing low-level keyboard hook or detection logic from Mouse Utilities could potentially be reused or adapted for CmdPal, reducing implementation complexity.
- Existing implementation: PowerToys Settings -> Mouse Utilities -> Find My Mouse -> Activation method (Double press Left Ctrl).

### Scenario when this would be used?

This feature would significantly lower the friction for launching commands, making CmdPal better than PowerToys Run.

### Supporting information

**Similar request for PowerToys Run:**
#3957
#7399
#13947
#15658
#17241
#22437

**Implemented in PowerToys "Find My Mouse":**
https://github.com/microsoft/PowerToys/blob/67d96b0a13e14118fb3ef6d238bbd788c256f919/src/modules/MouseUtils/FindMyMouse/FindMyMouse.cpp#L327

Start by reading the cited FindMyMouse.cpp implementation around line 327, then trace how CmdPal activation and settings are wired. Compare the existing double-press behavior with the requested modifier-key options; done means CmdPal can be configured to activate from a selected modifier double-tap.

Written by the indexing model from the issue text.