feat(planning): run interactive planning sessions via embedded ConPTY

Planning start/resume opened an external Windows Terminal (wt) window.
Route them through the embedded ConPTY Command Center pane instead, matching
the existing interactive-session UX (no external window).

- Extract bare planning arg builders (BuildPlanningStartArgs/ResumeArgs) from
  WindowsTerminalLauncher; the wt path still uses them (kept, not removed).
- InteractiveLaunchSpecService.BuildPlanningStart/Resume map a planning
  context into a LaunchSpec (planning args + env: MAX_THINKING_TOKENS,
  CLAUDEDO_PLANNING_TOKEN). Hub GetPlanningStart/ResumeLaunchSpec run
  StartAsync/ResumeAsync then return the spec.
- UI: OpenPlanningSession + the resume branch raise OpenPlanningConPtyRequested;
  the shell opens Mission Control and hosts a planning ConPTY pane.

Env is process-global by design (sequential human-paced sessions). wt planning
code retained. Tests added for the arg/env mapping.

src/ClaudeDo.Ui/Services/Interfaces/IWorkerClient.cs

@@ -82,6 +82,11 @@ public interface IWorkerClient : INotifyPropertyChanged
     /// <summary>Launch spec for an ad-hoc interactive session in an arbitrary directory --
     /// no task, no worktree.</summary>
     Task<LaunchSpec> GetAdHocLaunchSpecAsync(string directory, CancellationToken ct = default);
+    /// <summary>Starts a planning session and returns the launch spec for an embedded ConPTY
+    /// planning terminal (replaces StartPlanningSessionAsync's external wt window).</summary>
+    Task<LaunchSpec> GetPlanningStartLaunchSpecAsync(string taskId, CancellationToken ct = default);
+    /// <summary>Resumes a planning session and returns its embedded-ConPTY launch spec.</summary>
+    Task<LaunchSpec> GetPlanningResumeLaunchSpecAsync(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);

src/ClaudeDo.Ui/Services/WorkerClient.cs

@@ -519,6 +519,12 @@ public partial class WorkerClient : ObservableObject, IAsyncDisposable, IWorkerC
     public async Task<LaunchSpec> GetAdHocLaunchSpecAsync(string directory, CancellationToken ct = default)
         => await _hub.InvokeAsync<LaunchSpec>("GetAdHocLaunchSpec", directory, ct);
 
+    public async Task<LaunchSpec> GetPlanningStartLaunchSpecAsync(string taskId, CancellationToken ct = default)
+        => await _hub.InvokeAsync<LaunchSpec>("GetPlanningStartLaunchSpec", taskId, ct);
+
+    public async Task<LaunchSpec> GetPlanningResumeLaunchSpecAsync(string taskId, CancellationToken ct = default)
+        => await _hub.InvokeAsync<LaunchSpec>("GetPlanningResumeLaunchSpec", taskId, ct);
+
     public async Task<DiscardPlanningOutcome> DiscardPlanningSessionAsync(string taskId, bool dequeueQueuedChildren = false, CancellationToken ct = default)
         => await _hub.InvokeAsync<DiscardPlanningOutcome>("DiscardPlanningSessionAsync", taskId, dequeueQueuedChildren, ct);