fix: improve output format instruction following

Gemini suddenly stops responding in the json
schema we requested in the system prompt. Instead
it's generating normal text. Repeating the
schema in user prompt seems to fix the issue
for now.

app/agent.py

@@ -15,9 +15,20 @@ CONFIG = types.GenerateContentConfig(
         literature.search_medical_literature,
     ],
     system_instruction=(Path(__file__).parent / "system_instruction.txt").read_text(),
-    thinking_config=types.ThinkingConfig(include_thoughts=True),
+    thinking_config=types.ThinkingConfig(include_thoughts=True, thinking_budget=1024),
 )
 
+RESPONSE_FORMAT = """\
+
+Return in JSON matching this specification:
+
+Source = { "title": string, "url": str }
+Statement = { "text": string, "sources": array<Source> }
+Return: array<Statement>
+
+Do not return the response in a markdown code block.
+Do not include the citation in the `text` field."""
+
 SOURCE_TOOL_NAMES = {
     literature.search_medical_literature.__name__,
     dailymed.find_drug_set_ids.__name__,
@@ -81,7 +92,7 @@ def validate_response(response: types.GenerateContentResponse) -> models.Stateme
 def respond(client: genai.Client, query: str) -> models.Statements:
     resp = client.models.generate_content(
         model="gemini-2.5-flash-preview-05-20",
-        contents=query,
+        contents=query + RESPONSE_FORMAT,
         config=CONFIG,
     )
     return validate_response(resp)