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.Ui/Services/Interfaces/IWorkerClient.cs

@@ -87,6 +87,9 @@ public interface IWorkerClient : INotifyPropertyChanged
     // Picks up a task's Claude session in a real terminal window (--resume) — distinct
     // from OpenInteractiveTerminalAsync (the in-app streaming session).
     Task ResumeTaskInTerminalAsync(string taskId, CancellationToken ct = default);
+    /// <summary>Launch spec for an embedded ConPTY terminal to open an interactive session
+    /// in a task's worktree (same worktree prep as an autonomous run).</summary>
+    Task<LaunchSpec> GetInteractiveLaunchSpecAsync(string taskId, CancellationToken ct = default);
     Task ResumePlanningSessionAsync(string taskId, CancellationToken ct = default);
     Task<DiscardPlanningOutcome> DiscardPlanningSessionAsync(string taskId, bool dequeueQueuedChildren = false, CancellationToken ct = default);
     Task FinalizePlanningSessionAsync(string taskId, bool queueAgentTasks = true, CancellationToken ct = default);