refactor(recent): replace active-now tracking with recent session window

Replace persisted 'active now' tracking with 48-hour recency window
Remove Zustand ActiveNowStore and localStorage persistence
Simplify session sidebar data flow

packages/ui/src/stores/useActiveNowStore.ts

@@ -1,46 +0,0 @@
-import { create } from 'zustand';
-import type { Session } from '@opencode-ai/sdk/v2';
-import {
-  type ActiveNowEntry,
-  addActiveNowSession,
-  persistActiveNowEntries,
-  pruneActiveNowEntries,
-  readActiveNowEntries,
-} from '@/components/session/sidebar/activitySections';
-import { getSafeStorage } from './utils/safeStorage';
-
-type ActiveNowStore = {
-  entries: ActiveNowEntry[];
-  setEntries: (entries: ActiveNowEntry[]) => void;
-  addSession: (sessionId: string) => void;
-  prune: (sessionsById: Map<string, Session>) => void;
-};
-
-const safeStorage = getSafeStorage();
-
-export const useActiveNowStore = create<ActiveNowStore>((set, get) => ({
-  entries: readActiveNowEntries(safeStorage),
-  setEntries: (entries) => {
-    if (entries === get().entries) return;
-    set({ entries });
-    persistActiveNowEntries(safeStorage, entries);
-  },
-  addSession: (sessionId) => {
-    const next = addActiveNowSession(get().entries, sessionId);
-    if (next === get().entries) return;
-    set({ entries: next });
-    persistActiveNowEntries(safeStorage, next);
-  },
-  prune: (sessionsById) => {
-    const current = get().entries;
-    const pruned = pruneActiveNowEntries(current, sessionsById);
-    if (
-      pruned.length === current.length
-      && pruned.every((entry, index) => entry.sessionId === current[index]?.sessionId)
-    ) {
-      return;
-    }
-    set({ entries: pruned });
-    persistActiveNowEntries(safeStorage, pruned);
-  },
-}));