fix(native): restore safe handover by making launch_from_cache presentation-aware

- Reverted handle_open_file to use native.launch_from_cache for atomic copy support.
- Upgraded Electron main process to handle specialized launcher logic (LibreOffice/AppleScript) internally after the copy operation.
- Ensures absolute paths and file existence before triggering OS apps.

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

@@ -125,6 +125,9 @@
             open_file_status = 'opening_file';
             open_file_status_message = 'Opening Application';
 
+            // Phase 2/5: Use the atomic copy-and-launch operation.
+            // The main process handler (file_handlers.ts) now handles the 
+            // specialized LibreOffice/AppleScript logic internally after copying.
             const launch_result = await native.launch_from_cache({
                 cache_root,
                 hash: event_file_obj.hash_sha256,