- The legacy `LanMountainDesktop_Launcher` named-pipe startup progress channel is retired. Public IPC notifications and host exit codes are the only startup state sources.
- Normal Launcher launches must probe public IPC for an existing Host before starting a new Host process. Host no longer owns multi-instance policy, activation prompts, or the old single-instance pipe.
-`SecondaryActivationSucceeded` is a success terminal state. `SecondaryActivationFailed` and `RestartLockNotAcquired` may surface as failures only after public IPC recovery has failed.
- Launcher startup errors must use FluentAvalonia resources, Fluent icons, an InfoBar recovery hint, and copyable diagnostics instead of the old hard-coded dark panel.
### 6. Multi-instance behavior setting
- App settings include `MultiInstanceLaunchBehavior` with default `NotifyAndOpenDesktop`.
- General settings exposes the behavior under Basic Settings with four choices: restart app, open desktop silently, prompt only, and notify plus open desktop.
- Launcher reads the Host `settings.json` before a normal launch and applies the selected behavior when public IPC reports an existing Host.
-`PromptOnly` shows a Fluent Launcher prompt and does not open the desktop automatically.
-`NotifyAndOpenDesktop` activates the existing Host and shows the already-running notice from Launcher.
-`RestartApp` requests restart through public IPC and must not create a second Host if the restart request fails.