macos: Handle ctrl characters in IME input (#4854)

Fixes:
https://github.com/ghostty-org/ghostty/issues/4634#issuecomment-2573469532

This commit fixes two issues:

1. `libghostty` must not override ctrl+key inputs if we are in a preedit
state. This allows thigs like `ctrl+h` to work properly in an IME.

2. On macOS, when an IME commits text, we strip the control modifier
from the key event we send to libghostty. This is a bit of a hack but
this avoids triggering special ctrl+key handling.

macos/Sources/Ghostty/SurfaceView_AppKit.swift

@@ -828,8 +828,28 @@ extension Ghostty {
             var handled: Bool = false
             if let list = keyTextAccumulator, list.count > 0 {
                 handled = true
+
+                // This is a hack. libghostty on macOS treats ctrl input as not having
+                // text because some keyboard layouts generate bogus characters for
+                // ctrl+key. libghostty can't tell this is from an IM keyboard giving
+                // us direct values. So, we just remove control.
+                var modifierFlags = event.modifierFlags
+                modifierFlags.remove(.control)
+                if let keyTextEvent = NSEvent.keyEvent(
+                    with: .keyDown,
+                    location: event.locationInWindow,
+                    modifierFlags: modifierFlags,
+                    timestamp: event.timestamp,
+                    windowNumber: event.windowNumber,
+                    context: nil,
+                    characters: event.characters ?? "",
+                    charactersIgnoringModifiers: event.charactersIgnoringModifiers ?? "",
+                    isARepeat: event.isARepeat,
+                    keyCode: event.keyCode
+                ) {
                     for text in list {
-                    _ = keyAction(action, event: event, text: text)
+                        _ = keyAction(action, event: keyTextEvent, text: text)
+                    }
                 }
             }
 

src/apprt/embedded.zig

@@ -199,6 +199,11 @@ pub const App = struct {
             // This logic only applies to macOS.
             if (comptime builtin.os.tag != .macos) break :event_text event.text;
 
+            // If we're in a preedit state then we allow it through. This
+            // allows ctrl sequences that affect IME to work. For example,
+            // Ctrl+H deletes a character with Japanese input.
+            if (event.composing) break :event_text event.text;
+
             // If the modifiers are ONLY "control" then we never process
             // the event text because we want to do our own translation so
             // we can handle ctrl+c, ctrl+z, etc.