Exclude Time Travel history from backups

Skip usr/.time_travel during self-update user-data backups and add the same Time Travel shadow-history exclusion to default BackupService metadata.\n\nAdd focused regressions proving regular user files stay in backup coverage while Time Travel shadow repositories are omitted.

docker/run/AGENTS.md

@@ -22,6 +22,7 @@
 - Do not bake secrets, local `.env` values, or user data into the image.
 - Runtime startup must ensure `/a0/usr/uploads` exists before supervised services start.
 - Runtime startup raises the soft open-file limit toward `A0_NOFILE_LIMIT` (default `65535`) before supervisord starts, bounded by the container hard limit.
+- Self-update user-data backups skip Time Travel shadow history under `usr/.time_travel/` and transient Desktop agent state.
 
 ## Work Guidance
 

docker/run/fs/exe/self_update_manager.py

@@ -405,6 +405,11 @@ def should_exclude_from_usr_backup(
     logger: AttemptLogger,
 ) -> bool:
     parts = relative_dir.parts
+    if parts and parts[0] == ".time_travel":
+        logger.log(
+            f"Skipping Time Travel history during usr backup: {Path('usr') / relative_dir}"
+        )
+        return True
     if (
         len(parts) >= 6
         and parts[0] == "plugins"