### 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
Swift conveniently converts strings to UTF-8 encoded cstrings when
passing them to external functions, however our libghostty functions
also take a length and we were using String.count for that, which
returns the number of _characters_ not the byte length, which caused
searches with multi-byte characters to get truncated.
I went ahead and changed _all_ invocations that pass a string length to
use the utf-8 byte length even if the string is comptime-known and all
ASCII, just so that it's proper and if someone copies one of the calls
in the future for user-inputted data they don't reproduce this bug.
ref:
https://developer.apple.com/documentation/swift/string/counthttps://developer.apple.com/documentation/swift/stringprotocol/lengthofbytes(using:)
Move the search result counter (e.g. "1/30") inside the search text
field using an overlay, preventing layout shift when results appear.
This PR was authored with Claude Code.
Resolves Issue #8357
### Implementation
Following the existing `onResize` callback pattern in
`TerminalSplitTreeView`, I added an `onEqualize` callback to
`SplitView`. When a divider is double-tapped, the callback retrieves a
surface from that `TerminalView`'s `SplitTree` and calls `splitEqualize`
to equalize the entire tree.
### Context
There is an existing PR #8364 that implements this feature but uses
`focusedSurface`, which doesn't work for unfocused windows. Since that
PR has been inactive for a few months after requested changes, I've
implemented this alternative approach.
Credit to @liby for that initial implementation!
### AI Usage
I chatted with Claude Code in Plan mode to understand the relationship
between surfaces and the split tree/split views, but I wrote all the
code myself.
### Screenshot
https://github.com/user-attachments/assets/0efd70ef-c90e-4b50-b853-b05e2ca2be67
Partially fixes#8493.
After dictating some texts, the icon still appears above, but it will return to its right position after resizing or `\n` (saying newline, not hitting enter).
This behaviour is better than before, where the icon always appeared above.
### Reference:
9e905357bb/src/nsterm.m (L7426)
