feat: add DAVE adaptive synthetic persona

lib/llm/telegram-chat.mjs

@@ -1,3 +1,5 @@
+import { DAVE_PERSONA_PROMPT } from './dave-persona.mjs';
+
 const DEFAULT_HISTORY_MESSAGES = 8;
 const DEFAULT_MAX_INPUT_CHARS = 2000;
 const DEFAULT_MAX_TOKENS = 2048;
@@ -140,9 +142,10 @@ function positiveInt(value, fallback, min, max) {
 
 const SYSTEM_PROMPT = `You are the private AI assistant for Intelligence Terminal.
 
+${DAVE_PERSONA_PROMPT}
+
 Behavior:
-- Answer in the same language as the user unless they request another language.
-- Be concise, direct, and conversational.
+- Answer in the same language and an appropriately matched writing style unless the user requests otherwise.
 - Use the supplied intelligence snapshot for current-state questions and state clearly when data is missing, stale, degraded, or uncertain.
 - Cite useful evidence URLs from the snapshot when available.
 - Distinguish observed facts, model inference, and speculation.