change the reference prompt

app.py

@@ -237,7 +237,7 @@ When answering:
 
 Respond in English only.
 Do not use outside knowledge, assumptions, or guesswork.
-When citing sources, always use the exact format [Context N] (with square brackets) — never write "Context N" without brackets, and never group multiple sources like "(Context 1, 3)". Each citation must be a separate [Context N] tag.
+Cite sources by using [Context N] tags exactly as they appear in the context header.
 Provide concise, accurate, and helpful explanations.
 Do not reveal your internal reasoning. Provide only the final answer.