fix(launcher): resolve session selection hang and reactive header sync

- Optimized session navigation by switching from static data_url to reactive $page.url.\n- Fixed selection hang when entering the Launcher without an initial session ID.\n- Synchronized global header and idle logic with derived layout observables.\n- Streamlined prop passing to ensure clean state transitions during session switching.

src/routes/events/[event_id]/(launcher)/launcher/+layout.svelte

@@ -519,7 +519,6 @@
             class:hidden={$events_loc.launcher.hide__launcher_menu}
         >
             <Launcher_menu
-                data_url={data.url}
                 {lq__event_obj}
                 {lq__event_event_file_obj_li}
                 {lq__location_event_file_obj_li}