### Background
After #9344, the Ghostty theme won't change after switching systems', and reverting #9344 will bring back the issue it fixed.
The reason these two issues are related is because the scheme change is based on changes of `effectiveAppearance`, which is also affected by setting the window's `appearance` or changing `NSAppearance.currentDrawing()`.
### Changes
Instead of observing `effectiveAppearance`, we now explicitly update the color scheme of surfaces, so that we can control when it happens to avoid callback loops and redundant updates.
### Regression Tests
- [x] #8282
- [x] Reloading with `window-theme = light` should update Ghostty with the default dark theme with a dark window theme (break before [#83104ff](83104ff27a))
- [x] `window-theme = light \n macos-titlebar-style = native` should update Ghostty with the default dark theme with a light window theme
- [x] Reloading from the default config to `theme=light:3024 Day,dark:3024 Night \n window-theme = light`, should update Ghostty with the theme `3024 Day` with a light window theme (break on [#d39cc6d](d39cc6d478))
- [x] Using `theme=light:3024 Day,dark:3024 Night`; Switching the system's appearance should change Ghostty's appearance (break on [#d39cc6d](d39cc6d478))
- [x] Reloading from `theme=light:3024 Day,dark:3024 Night` with a light window theme to the default config, should update Ghostty with the default dark theme with a dark window theme
- [x] Reloading from the default config to `theme=light:3024 Day,dark:3024 Night \n window-theme=dark`, should update Ghostty with the theme `3024 Night` with a dark window theme
- [x] Reloading from `theme=light:3024 Day,dark:3024 Night \n window-theme=dark` to `theme=light:3024 Day,dark:3024 Night` with light system appearance, should update Ghostty from dark to light
- [x] Reload with quick terminal open
# Conflicts:
# macos/Sources/Features/Terminal/BaseTerminalController.swift
Maybe fixes#8736
I thought `windowDidLoad` was early on because its before the window is
shown but apparently not. Let's try `awakeFromNib` which is called
just after the window is loaded from the nib. It is hard to get any
earlier than that.
This fixes a small memory leak I found where the `SplitNode.Leaf` was
not being deinitialized properly when closing a split. It would get
deinitialized the next time a split was made or the window was closed,
so the leak wasn't big. The surface view underneath the split was also
properly deinitialized because we forced it, so again, the leak was
quite small.
But conceptually this is a big problem, because when we change the
surface tree we expect the deinit chain to propagate properly through
the whole thing, _including_ to the SurfaceView.
This fixes that by removing the `id(node)` call. I don't find this to be
necessary anymore. I don't know when that happened but we've changed
quite a lot in our split system since it was introduced. I'm also not
100% sure why the `id(node)` was causing a strong reference to begin
with... which bothers me a bit.
AI note: While I manually hunted this down, I started up Claude Code and
Codex in separate tabs to also hunt for the memory leak. They both
failed to find it and offered solutions that didn't work.
Mitchell Hashimoto