Fixes#1664
I previously asserted that we got exactly one run from CoreText because
I assumed that our run iterator was perfectly splitting runs for
CoreText. This assumption appears to be false and that seems okay.
The test case in this commit produces two runs that are directly next to
each other and there's no downside to simply iterating over them. So
this commit changes to iterate over the runs.
In korean input method on macos, it should simply return empty string.
Issue was created after https://github.com/mitchellh/ghostty/pull/1659.
```
gksr<BS> # 한ㄱ<BS>
```
'ㄱ' at the end should be removed with single <BS>, but for now
it requires two <bs> to remove 'ㄱ'.
Fixes#1656
When called as part of window restoration AppKit has a lock, so
NSAppearance changes need to be called async.
See deadlock:
```
Thread 1 Queue : com.apple.main-thread (serial)
0 0x000000018fd63fac in __ulock_wait ()
1 0x00000001069bf720 in _dlock_wait ()
2 0x00000001069bfaec in _dispatch_group_wait_slow ()
3 0x0000000106b5f5c4 in interposed_dispatch_group_wait ()
4 0x00000001937fb1f0 in NSCGSTransactionRunPreCommitActions_ ()
5 0x00000001938f1230 in -[_NSCGSTransaction synchronize] ()
6 0x00000001938f11ac in NSCGSTransactionSynchronize ()
7 0x000000019382ad30 in +[NSCGSWindow(NSCGSSpace) isAnyWindowOnAVisibleSpace:] ()
8 0x000000019382a968 in -[NSWindow _isInSomeVisibleSpace] ()
9 0x000000019382a8e4 in -[NSWindow isOnActiveSpace] ()
10 0x0000000193db8d98 in -[NSApplication(NSApplicationAppearance_Internal) _invalidateWindowAppearances] ()
11 0x00000001938f44d4 in -[NSApplication(NSAppearanceCustomization) setAppearance:] ()
12 0x0000000102c48050 in AppDelegate.syncAppearance() at /Users/mitchellh/code/go/src/github.com/mitchellh/ghostty/macos/Sources/App/macOS/AppDelegate.swift:412
13 0x0000000102c47840 in AppDelegate.configDidReload(_:) at /Users/mitchellh/code/go/src/github.com/mitchellh/ghostty/macos/Sources/App/macOS/AppDelegate.swift:380
14 0x0000000102c43c7c in AppDelegate.applicationDidFinishLaunching(_:) at /Users/mitchellh/code/go/src/github.com/mitchellh/ghostty/macos/Sources/App/macOS/AppDelegate.swift:110
```
