feat: add key-free demo mode replaying recorded fixtures

backend/app/adapters/anthropic/llm.py

@@ -112,7 +112,7 @@ class AnthropicRecommender:
         if parsed is None:
             raise RecommenderOutputError("Intent response contained no structured output")
         validated = IntentOutput.model_validate(parsed.model_dump())
-        return _to_intent(validated)
+        return to_intent(validated)
 
     async def stream_rerank(
         self,
@@ -125,7 +125,7 @@ class AnthropicRecommender:
     ) -> AsyncGenerator[RerankSelection]:
         """Yield each complete valid selection while the JSON is streaming."""
         schema = transform_schema(RerankOutput.model_json_schema())
-        parser = _RecommendationObjectParser()
+        parser = RecommendationObjectParser()
         async with self.client.messages.stream(
             model=self.settings.llm_model,
             max_tokens=self.settings.rerank_max_tokens,
@@ -166,8 +166,11 @@ class AnthropicRecommender:
             raise RecommenderOutputError("Rerank response returned too many selections")
 
 
-class _RecommendationObjectParser:
+class RecommendationObjectParser:
+    """Incrementally extract complete recommendation objects from JSON text."""
+
     def __init__(self) -> None:
+        """Create an empty parser for one rerank response."""
         self.complete_text = ""
         self._scan_index = 0
         self._object_start: int | None = None
@@ -177,6 +180,7 @@ class _RecommendationObjectParser:
         self._has_found_array = False
 
     def feed(self, text_delta: str) -> list[RerankSelectionOutput]:
+        """Consume a text delta and return newly completed selections."""
         self.complete_text += text_delta
         if not self._has_found_array:
             match = _RECOMMENDATION_ARRAY.search(self.complete_text)
@@ -231,7 +235,8 @@ class _RecommendationObjectParser:
             raise RecommenderOutputError("Rerank item failed validation") from error
 
 
-def _to_intent(output: IntentOutput) -> Intent:
+def to_intent(output: IntentOutput) -> Intent:
+    """Map validated intent output to the application domain."""
     return Intent(
         mood=tuple(output.mood),
         activity=output.activity,