feat: add unblock-nag detection and redirect

Keyword-based detection for users repeatedly asking to be unblocked in
chat. Fires an LLM-generated snarky redirect (with static fallback),
tracks per-user nag count with escalating sass, and respects a 30-min
cooldown. Configurable via config.yaml unblock_nag section.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

config.yaml

@@ -36,6 +36,11 @@ topic_drift:
   escalation_count: 3  # After this many reminds, DM the server owner
   reset_minutes: 60  # Reset off-topic count after this much on-topic behavior
 
+unblock_nag:
+  enabled: true
+  use_llm: true  # Generate redirect messages via LLM instead of static templates
+  remind_cooldown_minutes: 30  # Don't remind same user more than once per this window
+
 mention_scan:
   enabled: true
   scan_messages: 30       # Messages to scan per mention trigger