Make thread completion notifications reliable

[jln13x]

Summary

• persist a per-environment orchestration event cursor and replay missed turn completions after reconnects or renderer reloads
• queue native notifications in a durable outbox with deduplication and retry failed IPC or macOS deliveries
• wait for Electron notification acknowledgement and treat failed, closed, or timed-out delivery as unsuccessful
• cover project threads, standalone chats, reconnect, reload, disabled settings, deduplication, and native failure paths

Verification

• vp check
• vp run typecheck
• vp test apps/web/src/threadCompletionNotifications.test.ts apps/web/src/interactionSounds.test.ts apps/desktop/src/electron/ElectronNotification.test.ts apps/desktop/src/ipc/methods/window.test.ts
• production web and desktop build