do not process charCallback if control character was processed

Fixes #267

We have a mechanism `ignore_char` to ignore the `charCallback` exactly
once. It is guaranteed by all app runtimes that `keyCallback` is called
before `charCallback` and that they're called in order by key press
(you'll never get 3 `keyCallbacks` and then `charCallback` for the first
press).

We use this for example to ensure that if you bind `a` to something,
that we never actually print 'a', since the binding consumes it.

This commit sets `ignore_char` whenever we detect a key that should be
translated to a control character and written to the pty. As the comment
in the code states: we probably should've been doing this anyways. It is
a complete mystery why macOS behaves the way it does that caused us to
figure this out.

src/Surface.zig

@@ -1137,6 +1137,18 @@ pub fn keyCallback(
             };
         };
         if (char > 0) {
+            // We are handling this char so don't allow charCallback to do
+            // anything. Normally it shouldn't because charCallback should not
+            // be called for control characters. But, we found a scenario where
+            // it does: https://github.com/mitchellh/ghostty/issues/267
+            //
+            // In case that URL goes away: on macOS, after typing a dead
+            // key sequence, macOS would call `insertText` with control
+            // characters. Prior to calling a dead key sequence, it would
+            // not. I don't know. It doesn't matter, this is more correct
+            // anyways.
+            self.ignore_char = true;
+
             // Ask our IO thread to write the data
             var data: termio.Message.WriteReq.Small.Array = undefined;
             data[0] = @intCast(char);