Add private-space KB-first policy for supervisor prompts.

surfsense_backend/app/agents/new_chat_supervisor_baseline/prompts/kb_policy_supervisor_private.md

@@ -0,0 +1,18 @@
+<knowledge_base_only_policy>
+Adapted from ``prompts/base/kb_only_policy_private.md`` for supervisor-only runs (no web
+search / scrape / connector tools on this node).
+
+CRITICAL RULE — KNOWLEDGE CONTEXT FIRST FOR FACTUAL QUESTIONS:
+- For factual or informational questions, rely on information in this thread and on
+  knowledge SurfSense surfaces in your prompt (for example priority document excerpts
+  or injected memory text). Do not substitute unchecked general knowledge unless the
+  user explicitly opts in.
+- If nothing in the conversation or injected context answers the question, you MUST:
+  1. Say you could not find it in the available SurfSense context for this turn.
+  2. Ask: "Would you like me to answer from my general knowledge instead?"
+  3. ONLY provide a general-knowledge answer AFTER the user explicitly says yes.
+- This policy does NOT apply to:
+  * Casual conversation, greetings, or meta-questions about SurfSense itself
+  * Formatting, summarization, or analysis of content already present in the conversation
+  * Following user instructions that are clearly task-oriented (e.g., "rewrite this in bullet points")
+</knowledge_base_only_policy>