Add os_window_title to sessions

docs/sessions.rst

@@ -135,6 +135,8 @@ all the major keywords you can use in kitty session files:
     new_os_window
     # Set new window size to 80x24 cells
     os_window_size 80c 24c
+    # Set the --title for the new OS window
+    os_window_title my fancy os window
     # Set the --class for the new OS window
     os_window_class mywindow
     # Set the --name for the new OS window
@@ -291,6 +293,11 @@ documentation for them.
     Create a new tab with the specified title. If no title is specified, the
     title behaves just as for a regular tab in kitty.
 
+``os_window_title``
+    Set the title for the current OS Window. The OS Window will then always
+    have this title, it will not change based on the title of the currently active
+    window inside the OS Window.
+
 ``os_window_class``
     Set the class part of WM_CLASS or Wayland Application Id for the current OS Window
 

kitty/boss.py

@@ -456,7 +456,7 @@ class Boss:
             size_data = get_os_window_sizing_data(opts_for_size or get_options(), startup_session)
             wclass = wclass or getattr(startup_session, 'os_window_class', None) or self.args.cls or appname
             wname = wname or getattr(startup_session, 'os_window_name', None) or self.args.name or wclass
-            wtitle = override_title or self.args.title
+            wtitle = override_title or getattr(startup_session, 'os_window_title', None) or self.args.title
             window_state = window_state or getattr(startup_session, 'os_window_state', None)
             wstate = parse_os_window_state(window_state) if window_state is not None else None
             with startup_notification_handler(do_notify=startup_id is not None, startup_id=startup_id) as pre_show_callback:

kitty/session.py

@@ -92,6 +92,7 @@ class Session:
         self.os_window_class: str | None = None
         self.os_window_name: str | None = None
         self.os_window_state: str | None = None
+        self.os_window_title: str | None = None
         self.focus_os_window: bool = False
 
     @property
@@ -263,6 +264,8 @@ def parse_session(
                 ans.os_window_class = rest
             elif cmd == 'os_window_name':
                 ans.os_window_name = rest
+            elif cmd == 'os_window_title':
+                ans.os_window_title = rest
             elif cmd == 'os_window_state':
                 ans.os_window_state = rest
             elif cmd == 'resize_window':
@@ -339,6 +342,7 @@ def create_sessions(
     if args is not None:
         ans.os_window_class = args.cls
         ans.os_window_name = args.name
+        ans.os_window_title = args.title
     if special_window is None:
         cmd = args.args if args and args.args else resolved_shell(opts)
         from kitty.tabs import SpecialWindow