Introduce HostLaunchPlan and refine launch flow

Add HostLaunchPlan/HostLaunchPlanBuilder to encapsulate host path, package root, working dir, forwarded args and env; add unit tests for builder. Refactor LauncherFlowCoordinator to use HostLaunchPlan when starting hosts, improve IPC handling and startup logic (shorter soft/hard timeouts, more frequent reconnects and shell status polling, activation recovery via existing host). Move argument formatting and environment setup into the plan, include package/working/args metadata in start attempts. Update Commands to prefer ProcessPath for launcher base directory. App and Program: start single-instance activation listener earlier and harden ActivateMainWindow to handle shell initialization state and return richer activation status codes. SingleInstanceService: signal listener readiness (ManualResetEventSlim) and wait briefly when starting, and dispose it. Various logging and minor error handling improvements.

LanMountainDesktop.Launcher/Services/Commands.cs

@@ -166,7 +166,10 @@ internal static class Commands
             return Path.GetFullPath(configured);
         }
 
-        var baseDir = AppContext.BaseDirectory;
+        var launcherDir = Path.GetDirectoryName(Environment.ProcessPath);
+        var baseDir = Path.GetFullPath(!string.IsNullOrWhiteSpace(launcherDir)
+            ? launcherDir
+            : AppContext.BaseDirectory);
         
         // 发布版结构：Launcher 和 app-* 目录在同一目录
         // 检查当前目录是否有 app-* 子目录（发布版）