fix(room): require @ai mention to trigger AI response

- process_message_ai now returns early if no @ai mention is found
- Verify mentioned AI exists in the room before responding

libs/room/src/service/mod.rs

@@ -321,8 +321,48 @@ impl RoomService {
             return Ok(());
         };
 
-        let Some(ai_config) = self.get_room_ai_config(room_id).await? else {
+        // Extract mentioned AI model ID from content
-            return Ok(());
+        let mentioned_model_id = {
+            let mut found = None;
+            for cap in mention_bracket_re().captures_iter(&content) {
+                if let (Some(type_m), Some(id_m)) = (cap.get(1), cap.get(2)) {
+                    if type_m.as_str() == "ai" {
+                        if let Ok(uuid) = Uuid::parse_str(id_m.as_str().trim()) {
+                            found = Some(uuid);
+                            break;
+                        }
+                    }
+                }
+            }
+            if found.is_none() {
+                for cap in mention_tag_re().captures_iter(&content) {
+                    if let (Some(type_m), Some(id_m)) = (cap.get(1), cap.get(2)) {
+                        if type_m.as_str() == "ai" {
+                            if let Ok(uuid) = Uuid::parse_str(id_m.as_str().trim()) {
+                                found = Some(uuid);
+                                break;
+                            }
+                        }
+                    }
+                }
+            }
+            found
+        };
+
+        let model_id = match mentioned_model_id {
+            Some(id) => id,
+            None => return Ok(()), // No @ai mention, don't respond
+        };
+
+        // Verify the mentioned AI exists in this room
+        let ai_config = match room_ai::Entity::find()
+            .filter(room_ai::Column::Room.eq(room_id))
+            .filter(room_ai::Column::Model.eq(model_id))
+            .one(&self.db)
+            .await?
+        {
+            Some(c) => c,
+            None => return Ok(()), // Mentioned AI not in this room
         };
 
         let Some(lock_guard) =
@@ -337,23 +377,6 @@ impl RoomService {
             .one(&self.db)
             .await?
             .ok_or_else(|| RoomError::NotFound("Project not found".to_string()))?;
-
-        let mentioned_model_id = {
-            let mut found = None;
-            for cap in mention_bracket_re().captures_iter(&content) {
-                if let (Some(type_m), Some(id_m)) = (cap.get(1), cap.get(2)) {
-                    if type_m.as_str() == "ai" {
-                        if let Ok(uuid) = Uuid::parse_str(id_m.as_str().trim()) {
-                            found = Some(uuid);
-                            break;
-                        }
-                    }
-                }
-            }
-            found
-        };
-
-        let model_id = mentioned_model_id.unwrap_or(ai_config.model);
         let model = models::agents::model::Entity::find_by_id(model_id)
             .one(&self.db)
             .await?