'import' relative path issue when run symbol linked self-executbale justfile

I have these content in my justfile:
```just
#!/usr/bin/env -S just --working-directory . --justfile

import 'lib.just'
import 'config.just'
import 'template_var.just'
```
I can run the file normally. However, when I symbol linked file (for example `ln -sf`) and run the symbol link, it prompts `error: Could not find source file for import.`. (Note the symbol link is at the different directory than targeted justfile)

Reproduce the error using the shown justfile, its three imports, and a symbolic link located in another directory. Start by tracing how import source paths are resolved when just runs through a symlink, then verify the fix by running both the original justfile and the linked file and confirming that all imports load.

Written by the indexing model from the issue text.