feat: set auto-compact threshold to 165k tokens

Compact earlier to preserve more context fidelity before the window fills.

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

src/db.ts

@@ -149,15 +149,11 @@ function createSchema(database: Database.Database): void {
 
   // Add reply context columns if they don't exist (migration for existing DBs)
   try {
-    database.exec(
-      `ALTER TABLE messages ADD COLUMN reply_to_message_id TEXT`,
-    );
+    database.exec(`ALTER TABLE messages ADD COLUMN reply_to_message_id TEXT`);
     database.exec(
       `ALTER TABLE messages ADD COLUMN reply_to_message_content TEXT`,
     );
-    database.exec(
-      `ALTER TABLE messages ADD COLUMN reply_to_sender_name TEXT`,
-    );
+    database.exec(`ALTER TABLE messages ADD COLUMN reply_to_sender_name TEXT`);
   } catch {
     /* columns already exist */
   }