Rewrite static site generator from Gleam to Haskell

[Copilot]

Replaces Gleam-based static site generator with functionally equivalent Haskell implementation.

Changes

• New Haskell implementation (app/Main.hs, site-generator.cabal)

  • Parses content/index.djot config file (key-value pairs)
  • Generates HTML and CSS to dist/ directory
  • Exception handling with IOException

• CI/CD update (.github/workflows/deploy.yml)

  • Switched from erlef/setup-beam (Gleam) to haskell-actions/setup@v2
  • Build: cabal build → cabal run site-generator

• Test suite (test/Test.hs)

  • Verifies output file generation

• Cleanup

  • Removed Gleam files: gleam.toml, manifest.toml, src/, old tests
  • Updated .gitignore for Haskell artifacts (dist-newstyle/, *.hi, *.o)
  • Updated README.md with Haskell prerequisites and commands

Implementation notes

Parsing handles flexible whitespace with dropWhile isSpace to match Gleam's string.trim behavior:

parseConfig :: String -> [(String, String)]
parseConfig content = 
  let processLine line = case break (== ':') line of
        (key, ':':rest) -> Just (trim key, trim rest)
        _ -> Nothing
  in foldr (\line acc -> maybe acc (:acc) (processLine line)) [] (lines content)

Generated HTML/CSS output is byte-identical to original implementation.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Rewrite this in Haskell</issue_title>
<issue_description>Rewrite this in Haskell</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Rewrite this in Haskell #2

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