refactor(api): replace wildcard pattern with caseBabbageOnlyOrConwayEraOnwards

Improves exhaustiveness checking in parseInlineDatum by replacing the
`case (convert w :: ShelleyBasedEra era) of` pattern with a dedicated
case function for BabbageEraOnwards.

Changes:

1. Added caseBabbageOnlyOrConwayEraOnwards to Cardano.Api.Era.Internal.Case:
   - Distinguishes Babbage era from Conway+ eras
   - Provides compiler-enforced exhaustiveness checking
   - Follows existing pattern of other case functions in the module
   - Properly exported in module header

2. Updated parseInlineDatum in Cardano.Api.Tx.Internal.Output:
   - Replaced `case (convert w :: ShelleyBasedEra era)` with wildcard
   - Now uses caseBabbageOnlyOrConwayEraOnwards for explicit era handling
   - Preserves existing behavior: Babbage uses scriptDataJsonToHashable,
     Conway+ uses scriptDataFromJson
   - Updated documentation to reflect the improved design

Benefits:
- If a new era is added to BabbageEraOnwards, the compiler will catch
  any missing updates in caseBabbageOnlyOrConwayEraOnwards
- Eliminates wildcard pattern that could hide incomplete era handling
- Consistent with codebase pattern for era-based case analysis

All 37 TxOut JSON tests pass, confirming behavioral equivalence.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: newhoggy

cardano-api/src/Cardano/Api/Tx/Internal/Output.hs

@@ -496,9 +496,9 @@ instance IsShelleyBasedEra era => FromJSON (TxOut CtxTx era) where
     -- VALIDATION: When both hash and datum are present, we verify the datum hashes to the
     -- provided hash. This catches malformed JSON where they don't match.
     --
-    -- POTENTIAL ISSUE: The wildcard pattern (_ -> scriptDataFromJson) assumes all non-Babbage
-    -- eras in BabbageEraOnwards use scriptDataFromJson. If a future era needs different handling,
-    -- this must be updated to explicitly match all constructors.
+    -- DESIGN: Uses caseBabbageOnlyOrConwayEraOnwards to distinguish between Babbage (first function)
+    -- and Conway/Dijkstra (second function). This provides exhaustiveness checking - if a new era
+    -- is added to BabbageEraOnwards, the compiler will ensure it's handled.
     parseInlineDatum
       :: BabbageEraOnwards era
       -> Aeson.Object
@@ -508,15 +508,19 @@ instance IsShelleyBasedEra era => FromJSON (TxOut CtxTx era) where
       inlineDatum <- o .:? "inlineDatum"
       case (inlineDatum, inlineDatumHash) of
         (Just dVal, Just h) -> do
-          sData <- case (convert w :: ShelleyBasedEra era) of
-            ShelleyBasedEraBabbage ->
-              case scriptDataJsonToHashable ScriptDataJsonDetailedSchema dVal of
-                Left err -> fail $ "Error parsing TxOut JSON: " <> displayError err
-                Right hashableData -> return hashableData
-            _ ->
-              case scriptDataFromJson ScriptDataJsonDetailedSchema dVal of
-                Left err -> fail $ "Error parsing TxOut JSON: " <> displayError err
-                Right scriptData -> return scriptData
+          sData <-
+            caseBabbageOnlyOrConwayEraOnwards
+              -- Babbage case: use scriptDataJsonToHashable
+              ( case scriptDataJsonToHashable ScriptDataJsonDetailedSchema dVal of
+                  Left err -> fail $ "Error parsing TxOut JSON: " <> displayError err
+                  Right hashableData -> return hashableData
+              )
+              -- Conway+ case: use scriptDataFromJson
+              ( \_ -> case scriptDataFromJson ScriptDataJsonDetailedSchema dVal of
+                  Left err -> fail $ "Error parsing TxOut JSON: " <> displayError err
+                  Right scriptData -> return scriptData
+              )
+              w
           if hashScriptDataBytes sData /= h
             then fail "Inline datum not equivalent to inline datum hash"
             else return $ TxOutDatumInline w sData