feat(app): add zustand store for session state management

packages/app/src/stores/session-store.ts

@@ -0,0 +1,55 @@
+import { create } from "zustand";
+import type { SessionContextValue } from "@/contexts/session-context";
+
+// SessionData mirrors SessionContextValue so consumers can subscribe to a single source of truth.
+export type SessionData = SessionContextValue;
+
+interface SessionStore {
+  sessions: Record<string, SessionData>;
+  setSession: (serverId: string, data: SessionData) => void;
+  updateSession: (serverId: string, partial: Partial<SessionData>) => void;
+  clearSession: (serverId: string) => void;
+  getSession: (serverId: string) => SessionData | undefined;
+}
+
+export const useSessionStore = create<SessionStore>((set, get) => ({
+  sessions: {},
+  setSession: (serverId, data) => {
+    set((state) => ({
+      sessions: {
+        ...state.sessions,
+        [serverId]: data,
+      },
+    }));
+  },
+  updateSession: (serverId, partial) => {
+    set((state) => {
+      const existing = state.sessions[serverId];
+      const next: SessionData | undefined = existing
+        ? { ...existing, ...partial, serverId }
+        : (partial.serverId ? { ...(partial as SessionData), serverId } : undefined);
+
+      if (!next) {
+        return state;
+      }
+
+      return {
+        sessions: {
+          ...state.sessions,
+          [serverId]: next,
+        },
+      };
+    });
+  },
+  clearSession: (serverId) => {
+    set((state) => {
+      if (!(serverId in state.sessions)) {
+        return state;
+      }
+      const nextSessions = { ...state.sessions };
+      delete nextSessions[serverId];
+      return { sessions: nextSessions };
+    });
+  },
+  getSession: (serverId) => get().sessions[serverId],
+}));