Add minimal Cooklang parser with first tests

- Create Roux.Parser with parseCookFile (splits paragraphs, treats
  each as a plain-text step, no metadata parsing yet)
- Add emptyMetadata to Roux.Types for convenience
- Add test dependencies: hspec, tasty-golden, tasty-hspec
- Add ParserSpec with 4 tests covering single step, multiple steps,
  empty input, and whitespace trimming
- Wire ParserSpec into test runner via tasty-hspec

src/Roux/Parser.hs

@@ -0,0 +1,39 @@
+{- | Parser for Cooklang (.cook) recipe files.
+
+Currently a minimal placeholder that splits input into paragraphs and
+treats them as plain-text steps.  Proper inline parsing (ingredients,
+cookware, timers, …) and metadata support will be added incrementally.
+-}
+module Roux.Parser
+    ( parseCookFile
+    ) where
+
+import Data.List.NonEmpty (NonEmpty ((:|)))
+import Data.Text (Text)
+import qualified Data.Text as T
+
+import Roux.Types
+
+-- | Parse a complete @.cook@ file into a 'Recipe'.
+--
+-- Returns 'Left' with an error message on invalid input (currently never
+-- — the placeholder always succeeds).
+parseCookFile :: Text -> Either String Recipe
+parseCookFile input =
+    let paragraphs = filter (not . T.null) (map T.strip (T.splitOn "\n\n" (T.strip input)))
+     in case paragraphs of
+            [] ->
+                Right Recipe
+                    { recipeMetadata = emptyMetadata
+                    , recipeSections = Section Nothing (Step [] :| []) :| []
+                    }
+            (p : ps) ->
+                Right Recipe
+                    { recipeMetadata = emptyMetadata
+                    , recipeSections = Section Nothing (stepFromText p :| fmap stepFromText ps) :| []
+                    }
+
+-- | Turn a paragraph of text into a single 'Step' containing nothing but
+-- 'StepText'.  This is a placeholder until inline parsing is implemented.
+stepFromText :: Text -> Step
+stepFromText t = Step [StepText t]