gtk: add comments about C API types to sync

src/terminal/osc.zig

@@ -204,6 +204,7 @@ pub const Command = union(enum) {
     };
 
     pub const ProgressReport = struct {
+        // sync with ghostty_terminal_osc_command_progressreport_state_e in include/ghostty.h
         pub const State = enum(c_int) {
             remove,
             set,
@@ -215,6 +216,7 @@ pub const Command = union(enum) {
         state: State,
         progress: ?u8 = null,
 
+        // sync with ghostty_terminal_osc_command_progressreport_s in include/ghostty.h
         pub const C = extern struct {
             state: c_int,
             progress: i8,