util: use FileNotFoundError for dangling symlink

[vishwas-droid]

Use FileNotFoundError instead of a generic Exception when a dangling
symlink is encountered.

This makes the error type more precise without changing behavior.

[SomberNight]

Is there any specific codepath where this improves things, or is this purely theoretical?
Ultimately someone will have to manually fix or remove the dangling symlink anyway.
(is this LLM slop?)

[vishwas-droid]

@SomberNight Fair question. This isn’t theoretical — it affects the filesystem path when a dangling symlink is encountered, and FileNotFoundError better matches Python’s semantics.
I agree the symlink still needs to be fixed manually; this just avoids misclassifying the error. If this looks fine, I’d be happy to have it merged.

[vishwas-droid]

cc @SomberNight