HLS seems to require a library stanza in the cabal file

## Environment

OS: NixOS
GHC Version: 9.4.8
Cabal Version: 3.10.2.1
HLS Version: 2.4.0.0

Everything is installed via a nix flake. Here is my project at the time of issue submission: https://github.com/Rotaerk/vulkanSandbox/tree/85d04fd4a834000cb47a7992207f8c74c5028428

## What's wrong?

Within the repository root, I run `nix develop`, which brings cabal, ghc, and HLS among other things into my path. I navigate into the VulkanSandbox directory, and run `haskell-language-server-wrapper`. When I do, it discovers all 14 of my source files, but fails to load every one, indicating that I need to add them to other-modules or exposed-modules in the cabal file. But they are already there.

The cabal file only has two stanzas: a common and an executable. I noticed that if I change the executable stanza into a library (and removed main-is), suddenly HLS is able to load the source files.

I also noticed that it works if I rename the executable stanza to VulkanSandboxExe, and then _add_ a library stanza to it, such as:
```
library
import: common
```

Note: I tested and confirmed that renaming the executable stanza alone was not enough.

Did I miss something in the HLS documentation about requiring library stanzas?