feat(interactive): worker launch-spec for embedded ConPTY sessions

Adds InteractiveLaunchSpecService + GetInteractiveLaunchSpec hub method that
prepares a task worktree (session-skills seeding, run env) and returns a
LaunchSpec {cwd,exe,args,env} for a UI-hosted ConPTY terminal. Reuses
ISessionSkillSeeder, TaskRunner.UnionSkillNames, and WindowsTerminalLauncher
resume-arg/resolve logic. Guards mirror ResumeTaskInTerminal; a never-run task
yields a fresh-start spec instead of an error.

src/ClaudeDo.Worker/Program.cs

@@ -77,6 +77,7 @@ builder.Services.AddSingleton<PendingQuestionRegistry>();
 builder.Services.AddSingleton<IRepoCloner, GitRepoCloner>();
 builder.Services.AddSingleton<ISessionSkillRegistry, SessionSkillRegistry>();
 builder.Services.AddSingleton<ISessionSkillSeeder, SessionSkillSeeder>();
+builder.Services.AddSingleton<IInteractiveLaunchSpecService, InteractiveLaunchSpecService>();
 builder.Services.AddSingleton<TaskRunner>();
 builder.Services.AddSingleton<WorktreeMaintenanceService>();
 builder.Services.AddSingleton<TaskResetService>();