fix: quick terminal CPU spikes

[dmehala]

Description

The following code is causing an infinite loop that causes a CPU spikes until the quick terminal is displayed:

ghostty/macos/Sources/Features/QuickTerminal/QuickTerminalController.swift

Lines 314 to 317 in 87bd0bb

	guard window.isVisible else {
	// Weak window so that if the window changes or is destroyed we aren't holding a ref
	DispatchQueue.main.async { [weak self] in self?.syncAppearance(config) }
	return

Reproduce steps

1. Open Ghostty.
2. Open the Quick Terminal.
3. Close the Quick Terminal.
4. Reload the configuration (Ghostty > Reload Configuration or shift+cmd+,).
5. Observe CPU spike.

Fix

Now, syncAppearance doesn't postpone the process until it can be consumed, and the appearance is synchronized once the animation is done and the quick terminal is visible.

Fixes #3998