Prepare for multi-package repository.

[jonathanknowles]

No description provided.

[Copilot]

Pull Request Overview

This PR prepares the repository for a multi-package setup through modifications to the GitHub Actions build workflow. Key changes include:

• Adding a conditional execution for the Documentation (Generation) step based on the operating system and GHC version.
• Replacing the "cabal haddock" command with "cabal haddock-project" with new flags.
• Removing the file move command in the Documentation (Staging) step.

Files not reviewed (1)

• cabal.project: Language not supported

Comments suppressed due to low confidence (2)

.github/workflows/build.yml:108

• The added condition restricts execution to only ubuntu-latest and GHC 9.12. Confirm this is intended for consistent behavior across all intended environments or update the condition accordingly.

if: |
            matrix.os == 'ubuntu-latest'
            && matrix.ghc == '9.12'

.github/workflows/build.yml:121

• Removing the move command may lead to issues if downstream steps still expect the documentation in the previous build directory location. Verify that 'cabal haddock-project' outputs documentation directly into the 'gh-pages' directory as intended.

mv ${{ env.cabal-build-dir }}/build/*/*/*/doc/html/* gh-pages