fix(FN-4804): sync quick chat session and room selection

- Clear the active chat room when switching Quick Chat to a direct session
- Keep the hidden session dropdown value and initial-session state aligned with room selection changes
- Add dashboard regression coverage for switching from a room back to a direct chat and include a CLI patch changeset

Fusion-Task-Id: FN-4804

packages/dashboard/app/components/QuickChatFAB.tsx

@@ -1785,6 +1785,10 @@ export function QuickChatFAB({
       return;
     }
 
+    if (chatRoomsEnabled && roomsState.activeRoom) {
+      roomsState.selectRoom(null);
+    }
+
     markRead("direct", selectedSession.id, selectedSession.lastMessageAt ?? selectedSession.updatedAt);
     hasAppliedInitialSessionRef.current = true;
 
@@ -1798,12 +1802,13 @@ export function QuickChatFAB({
 
     void selectSession(selectedSession);
     setSessionMenuOpen(false);
-  }, [markRead, selectSession, sessions]);
+  }, [chatRoomsEnabled, markRead, roomsState, selectSession, sessions]);
 
   const handleRoomSwitch = useCallback((roomId: string) => {
     const selectedRoom = roomsState.rooms.find((room) => room.id === roomId);
     markRead("room", roomId, selectedRoom?.updatedAt);
     roomsState.selectRoom(roomId);
+    hasAppliedInitialSessionRef.current = true;
     setSessionMenuOpen(false);
   }, [markRead, roomsState]);
 
@@ -2539,7 +2544,12 @@ export function QuickChatFAB({
           <div className="quick-chat-panel-agent-select" data-testid="quick-chat-session-select">
             <div className="quick-chat-session-menu" ref={sessionMenuRef}>
               <label htmlFor="quick-chat-session-dropdown-trigger" className="visually-hidden">Select session</label>
-              <input type="hidden" data-testid="quick-chat-session-dropdown" value={activeSession?.id ?? ""} readOnly />
+              <input
+                type="hidden"
+                data-testid="quick-chat-session-dropdown"
+                value={showRoomGroups && roomsState.activeRoom ? "" : activeSession?.id ?? ""}
+                readOnly
+              />
               <button
                 id="quick-chat-session-dropdown-trigger"
                 type="button"

packages/dashboard/app/components/__tests__/QuickChatFAB.test.tsx

@@ -1,3 +1,4 @@
+import { useState } from "react";
 import { beforeEach, describe, expect, it, vi } from "vitest";
 import { fireEvent, render, screen, waitFor } from "@testing-library/react";
 import type { Agent } from "../../api";
@@ -454,6 +455,53 @@ describe("QuickChatFAB session-first UX", () => {
     expect(screen.getByTestId("quick-chat-input")).toHaveAttribute("placeholder", "Message GPT-4o");
   });
 
+  it("FN-4804: switching from an active room to a direct session clears room display state", async () => {
+    const room = {
+      id: "room-1",
+      name: "engineering",
+      slug: "engineering",
+      memberCount: 2,
+      createdAt: new Date().toISOString(),
+      updatedAt: new Date().toISOString(),
+    };
+
+    mockUseAppSettings.mockReturnValue({ experimentalFeatures: { chatRooms: true } } as ReturnType<typeof useAppSettings>);
+    mockUseChatRooms.mockImplementation(() => {
+      const [activeRoom, setActiveRoom] = useState(room);
+      return {
+        rooms: [room],
+        roomsLoading: false,
+        roomsError: null,
+        activeRoom,
+        activeRoomMembers: [],
+        messages: [],
+        messagesLoading: false,
+        selectRoom: (roomId: string | null) => {
+          setActiveRoom(roomId ? room : null);
+        },
+        createRoom: vi.fn(),
+        deleteRoom: vi.fn(),
+        sendRoomMessage: vi.fn(),
+        refreshRooms: vi.fn(),
+      };
+    });
+
+    render(<QuickChatFAB addToast={vi.fn()} projectId="proj-1" />);
+    fireEvent.click(screen.getByTestId("quick-chat-fab"));
+
+    expect(await screen.findByTestId("quick-chat-input")).toHaveAttribute("placeholder", "Message #engineering");
+    expect(screen.getByTestId("quick-chat-session-dropdown")).toHaveValue("");
+
+    fireEvent.click(screen.getByTestId("quick-chat-session-dropdown-trigger"));
+    fireEvent.click(screen.getByTestId("quick-chat-session-option-session-agent"));
+
+    await waitFor(() => {
+      expect(screen.getByTestId("quick-chat-session-dropdown")).toHaveValue("session-agent");
+      expect(screen.getByTestId("quick-chat-input")).toHaveAttribute("placeholder", "Message Agent One");
+      expect(screen.getByTestId("quick-chat-session-dropdown-trigger")).not.toHaveTextContent("#engineering");
+    });
+  });
+
   describe("FN-4708 room reflection", () => {
     it("shows room placeholder and room tag when an active room exists", async () => {
       mockUseAppSettings.mockReturnValue({ experimentalFeatures: { chatRooms: true } } as ReturnType<typeof useAppSettings>);