Correct way to build a project in order to have Haddocks displayed on hover

## Your environment

haskell-language-server version: 2.7.0.0
editor: neovim

## What's wrong?

It appears that the haddocks of an identifier are unreliably shown.

For a local identifier, no problem


But for dependencies it's not a granted.


I have a `cabal.project` file with the following:

```cabal
packages: ./
with-compiler: ghc-9.4
documentation: True

package *
documentation: True
```

What am I missing? I thought I had covered all the cases?

### Debug information

Build log:

```bash

Build profile: -w ghc-9.4.8 -O1
In order, the following will be built (use -v for more details):
- os-string-2.0.2 (lib) (requires build)
- hashable-1.4.4.0 (lib) (requires build)
- unordered-containers-0.2.20 (lib) (requires build)
- relude-1.2.1.0 (lib) (requires build)
- cabaltest-0.1.0.0 (lib) (dependency rebuilt)
- cabaltest-0.1.0.0 (exe:cabaltest) (dependency rebuilt)
Starting os-string-2.0.2 (lib)
Building os-string-2.0.2 (lib)
Haddock os-string-2.0.2 (lib)
Installing os-string-2.0.2 (lib)
Completed os-string-2.0.2 (lib)
Starting hashable-1.4.4.0 (lib)
Building hashable-1.4.4.0 (lib)
Haddock hashable-1.4.4.0 (lib)
Installing hashable-1.4.4.0 (lib)
Completed hashable-1.4.4.0 (lib)
Starting unordered-containers-0.2.20 (lib)
Building unordered-containers-0.2.20 (lib)
Haddock unordered-containers-0.2.20 (lib)
Installing unordered-containers-0.2.20 (lib)
Completed unordered-containers-0.2.20 (lib)
Starting relude-1.2.1.0 (lib)
Building relude-1.2.1.0 (lib)
Haddock relude-1.2.1.0 (lib)
Installing relude-1.2.1.0 (lib)
Completed relude-1.2.1.0 (lib)
Preprocessing library for cabaltest-0.1.0.0..
Building library for cabaltest-0.1.0.0..
Preprocessing library for cabaltest-0.1.0.0..
Running Haddock on library for cabaltest-0.1.0.0..
50% ( 1 / 2) in 'MyLib'
Missing documentation for:
Module header

src/MyLib.hs:14:1: warning: [-Wunused-top-binds]
Defined but not used: ‘test’
|
14 | test = someFunc
| ^^^^
Documentation created:
/home/hecate/Téléchargements/test/cabal-test/dist-newstyle/build/x86_64-linux/ghc-9.4.8/cabaltest-0.1.0.0/doc/html/cabaltest/
Preprocessing executable 'cabaltest' for cabaltest-0.1.0.0..
Building executable 'cabaltest' for cabaltest-0.1.0.0..
[2 of 2] Linking /home/hecate/Téléchargements/test/cabal-test/dist-newstyle/build/x86_64-linux/ghc-9.4.8/cabaltest-0.1.0.0/x/cabaltest/build/cabaltest/cabaltest [Library changed]
```

Reproduce the hover behavior in Neovim using the reported haskell-language-server version and the shown cabal.project settings. Compare local identifiers with dependency identifiers, using the build log to confirm Haddock generation. Done means dependency Haddock documentation appears reliably on hover, with the required build configuration or failure condition documented.

Written by the indexing model from the issue text.