just doctor should detect if there are two competing .sdd folders in the $game_dir used by just link, even if one is in a subfolder, and warn about the risk

(e.g. both Beyond-All-Reason.sdd and BAR.sdd co-existing in /home/user/.var/app/info.beyondallreason.bar/data/games/ )

Steps to reproduce:
1. run `just setup init` etc, making sure to pull down the Beyond-All-Reason folder
2. run `just link create bar` to create a symlink
3. ensure in the repo folder for Beyond-All-Reason, you have changed to the `master` branch
4. manually copy (i.e. with rsync or filecopy or something) the Beyond-All-Reason folder into $GAME_DIR, renaming it to tmp_archive/BAR.sdd (folder nesting)
5. in the repo folder for Beyond-All-Reason, change to a branch that you expect to see gameplay changes from
6. start the game
7. be confused as to why you are seeing the game as though it were pointing at the master branch, rather than the feature branch

Issue: If both exist, even in a child directory, Spring engine appears to prefer to select BAR.sdd rather than Beyond-All-Reason.sdd (more research needed), leading to confusion as to why symlink folder changes are not being used by the game engine.

Expected behavior: `just doctor` detects and warns about this situation; and recommends the user delete one or both of the folders and try again

_(I thought the impromptu folder nesting (namely `tmp_archive/BAR.sdd` would save me from exactly this "two things in the same folder" issue, but apparently not.... That was a longer-than-desired debug session with DeepSeek v4 Pro...)_

Start at the `just doctor` entry point and inspect how it examines `$GAME_DIR`, then reproduce the setup and link steps from the issue with both `Beyond-All-Reason.sdd` and nested `tmp_archive/BAR.sdd` present. Done means `just doctor` warns about competing `.sdd` folders, including nested ones, and recommends deleting one or both before retrying.

Written by the indexing model from the issue text.