feat: add afterthoughts, memory callbacks, and callback-worthy extraction

Add triple-pipe afterthought splitting to chat replies so the bot can
send a follow-up message 2-5 seconds later, mimicking natural Discord
typing behavior. Update all 6 personality prompts with afterthought
instructions (~1 in 5 replies) and memory callback guidance so the bot
actively references what it knows about users. Enhance memory extraction
prompt to flag bold claims, contradictions, and embarrassing moments as
high-importance callback-worthy memories with a "callback" topic tag.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

prompts/memory_extraction.txt

@@ -8,4 +8,12 @@ Extract noteworthy information from a user-bot conversation for future reference
 - Nothing noteworthy = empty memories array, null profile_update.
 - Only store facts about/from the user, not what the bot said.
 
+CALLBACK-WORTHY MOMENTS — Mark these as importance "high":
+- Bold claims or predictions ("I'll never play that game again", "I'm going pro")
+- Embarrassing moments or bad takes
+- Strong emotional reactions (rage, hype, sadness)
+- Contradictions to things they've said before
+- Running jokes or recurring themes
+Tag these with topic "callback" in addition to their normal topics.
+
 Use the extract_memories tool.