fix(workspace): add trailing slash to session path prefix

Prevents session path prefix collisions where "/sessions/abc" could
incorrectly match "/sessions/abc123" when using startswith filtering.
Now uses "/sessions/abc/" to ensure exact session boundary matching.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

autogpt_platform/backend/backend/util/workspace.py

@@ -102,8 +102,9 @@ class WorkspaceManager:
             # Resolve the provided path with session scoping
             return self._resolve_path(path)
         elif self.session_path:
-            # Default to session folder
-            return self.session_path
+            # Default to session folder with trailing slash to prevent prefix collisions
+            # e.g., "/sessions/abc" should not match "/sessions/abc123"
+            return self.session_path.rstrip("/") + "/"
         else:
             # No session context, use path as-is
             return path