[BUGFIX] Unfocus Chart Editor dropdown after selecting item

[VICK-sys]

Linked Issues

Fixes #2956

Description

Fixes the chart editor input lockout that occurred when a HaxeUI toolbox field had focus (blue outline). After interacting with a field, playtesting with the toolbox open,
and reopening the toolbox, the field's focus was auto-restored, and isHaxeUIFocused returning true gated all chart editor input (scroll, note placement, playtest hotkey,
etc.).

The fix: in ChartEditorToolboxHandler.showToolbox and .hideToolbox, directly call IFocusable.focus = false on the currently-focused element via
FocusManager.instance.focus. This bypasses HaxeUI's set_focus(null) API, which has an asymmetric implementation: get_focus walks all root components, but
set_focus(null) only clears _lastFocuses for Screen.instance.topComponent, so focus living on a non-top root (like a dialog) can't be cleared through it.

Screenshots/Videos

Demo.Video.mp4

[Hundrec]

This bug has bothered me forever!

The PR's behavior is a big improvement, as it allows left clicks to unfocus the dropdown.
However, right clicking and scrolling is still gated until you left click.

The PR would be perfect if you fixed this too!

[VICK-sys]

This bug has bothered me forever!

The PR's behavior is a big improvement, as it allows left clicks to unfocus the dropdown. However, right clicking and scrolling is still gated until you left click.

The PR would be perfect if you fixed this too!

I'm on it