I tried setting up the extension on an existing project. The directory has a file at .eclipse/.bazelproject. I'm using version 1.25.101230444.
~/project ± ● main
❯ ls -all .eclipse
total 8
drwxr-xr-x@ 3 dan staff 96 Feb 16 17:14 .
drwxr-xr-x 24 dan staff 768 Feb 16 17:14 ..
-rw-rw-rw-@ 1 dan staff 121 Feb 16 18:14 .bazelproject