feat(FN-4583): complete Step 1 — add chat room message tail ordering

Fusion-Task-Id: FN-4583
Fusion-Task-Lineage: 4d9b088d-a705-4376-b547-15b37e5370aa

packages/core/src/__tests__/chat-store.rooms.test.ts

@@ -146,6 +146,25 @@ describe("ChatStore — rooms (FN-3805..FN-3811 contract)", () => {
       expect(store.listRoomMessagesSince(room.id, new Date().toISOString())).toEqual([]);
     });
 
+    it("returns newest limited room window when order is desc while preserving ascending output", () => {
+      const room = store.createRoom({ name: "window-test" });
+
+      for (let i = 1; i <= 107; i += 1) {
+        store.addRoomMessage(room.id, { role: "user", content: `message-${i}` });
+      }
+
+      const newestWindow = store.getRoomMessages(room.id, { limit: 100, order: "desc" });
+      expect(newestWindow).toHaveLength(100);
+      expect(newestWindow[0]?.content).toBe("message-8");
+      expect(newestWindow.at(-1)?.content).toBe("message-107");
+      expect(newestWindow.some((message) => message.content === "message-1")).toBe(false);
+
+      const legacyWindow = store.getRoomMessages(room.id, { limit: 100 });
+      expect(legacyWindow).toHaveLength(100);
+      expect(legacyWindow[0]?.content).toBe("message-1");
+      expect(legacyWindow.at(-1)?.content).toBe("message-100");
+    });
+
     it("keeps cross-room and direct-vs-room histories isolated", () => {
       const session = store.createSession({ agentId: "agent-1" });
       store.addMessage(session.id, { role: "user", content: "direct" });

packages/core/src/chat-store.ts

@@ -926,14 +926,16 @@ export class ChatStore extends EventEmitter<ChatStoreEvents> {
       params.push(filter.before);
     }
 
+    const order = filter?.order === "desc" ? "DESC" : "ASC";
     const rows = this.db.prepare(`
       SELECT * FROM chat_room_messages
       WHERE ${whereClauses.join(" AND ")}
-      ORDER BY createdAt ASC
+      ORDER BY createdAt ${order}
       LIMIT ? OFFSET ?
     `).all(...params, filter?.limit ?? 100, filter?.offset ?? 0) as ChatRoomMessageRow[];
 
-    return rows.map((row) => this.rowToRoomMessage(row));
+    const normalizedRows = filter?.order === "desc" ? [...rows].reverse() : rows;
+    return normalizedRows.map((row) => this.rowToRoomMessage(row));
   }
 
   listRoomMessagesSince(

packages/core/src/chat-types.ts

@@ -263,4 +263,5 @@ export interface ChatRoomMessagesFilter {
   limit?: number;
   offset?: number;
   before?: string;
+  order?: "asc" | "desc";
 }