[Bug] Timoni cannot handle symlinks in `cue.mod`

[jmgilman]

Steps to reproduce:

1. Create a new Timoni module
2. Define a custom CUE module somewhere else on the local filesystem
3. Symlink the custom CUE module somewhere in the Timoni module under cue.mod/pkg
4. Integrate the custom CUE module in the Timoni module somewhere
5. Attempt to build the Timoni module and get an error stating the custom CUE module cannot be found

This is becoming an increasingly common use-case as CUE module development progresses. Currently, the CUE module system doesn't have something similar to Go's replace directive, however, it does explicitly support symlinking modules into cue.mod. To give a more clear example:

timoni build -f debug_values.cue test .   # This fails

cue cmd -t debug -t name=test -t namespace=test -t mv=1.0.0 -t kv=1.28.0 build  # This does not

So, calling CUE directly builds the module without issue. However, Timoni reports:

timoni.sh/blueprint@v0:main.timoni.sh/blueprint/config: import failed: import failed: cannot find package "mymod/mypackage": cannot find module providing package mymod/mypkg:
    ./timoni.cue:9:2
    ./config/config.cue:5:2

Where cue.mod/pkg/mymod is symlinked to a CUE module folder exposing a mypkg package.