Launcher Slow-Startup And Startup Visual Addendum

New startup timing contract

30s is a soft timeout, not a failure threshold.
After 30s, if the desktop process is still alive or Public IPC is connected, Launcher must stay in a waiting state and must not start another host process.
120s is the hard timeout.
Before returning desktop_not_visible, Launcher must attempt one foreground recovery through ActivateMainWindowAsync().

Launcher persists the current startup attempt in %LocalAppData%\LanMountainDesktop\.launcher\state\startup-attempt.json.
A second Launcher process must attach to a live pending attempt instead of calling Process.Start() again.
Closing the splash window does not cancel startup; it transitions the attempt into detached waiting and preserves recovery state for the next Launcher run.

EnableSlideTransition = true forces StartupVisualMode.SlideSplash and automatically disables fade.
EnableSlideTransition = false && EnableFadeTransition = false resolves to StartupVisualMode.StaticSplash.
EnableSlideTransition = false && EnableFadeTransition = true resolves to StartupVisualMode.Fade.

The hidden Launcher debug menu owns the splash image picker.
Saving an image copies it into .Launcher as Launcher Picture.<ext> and clears the in-memory image cache.
Invalid, unsupported, or oversized images must not overwrite the existing managed image.
Splash image rendering uses Uniform fitting so the full image remains visible.
The self-drawn Splash shell uses fixed Fluent corner tokens: 8px outer radius and 4px control radius.

If the host process is still alive at failure time, the failure dialog must prefer:
- Activate
- Wait
- Open Logs
- Exit
Retry is only valid when Launcher is not about to create a duplicate desktop process.

Startup attempts are now reserved before host launch, so concurrent Launchers cannot all reach Process.Start().
A live coordinator is identified by CoordinatorPid, CoordinatorPipeName, and a heartbeat newer than 10s.
Secondary Launchers send activate-desktop or attach to the coordinator pipe and then exit with the coordinator status.
If Host Public IPC is already available during a normal launch, Launcher activates the existing desktop and does not start a new host process.
Public shell status now reports tray readiness and taskbar-entry usability separately, allowing Launcher to distinguish "running but hidden" from "not recoverable".