test(workflow): add symlink loop detection tests for LoadWorkflowFile

[watany-dev]

Add comprehensive tests to verify that LoadWorkflowFile properly handles
circular symlinks during YAML file loading:

• Self-referencing symlink (file.yml -> file.yml)
• Circular symlink chain (a.yml -> b.yml -> a.yml)
• Deep symlink chain (10-link circular chain)
• Symlink through directories with loop
• Relative symlink loop (./current.yml -> ./current.yml)
• Triple symlink loop (x.yml -> y.yml -> z.yml -> x.yml)
• Valid symlink to real file (positive test case)

These tests ensure the OS-level symlink loop detection ("too many levels
of symbolic links" error) is properly surfaced and that the function
does not hang when encountering circular references.