Addresses #10812 Release Notes: - Launching an empty already-running Zed application now behaves like a regular startup and respects the user `resume_on_startup` setting. ([#10812](https://github.com/zed-industries/zed/issues/10812)). See attached showcase which highlights how the previous project can now be re-opened through both "quit" and "close window". This has a noticeable performance benefit on startup/project resume time. This should also make the behaviour of closing/opening an application consistent between macOS/Linux/Windows. https://github.com/zed-industries/zed/assets/22855292/9c37ba31-ce0a-4c3d-940d-a56e3347e64a