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.

tests/ClaudeDo.Worker.Tests/Runner/InteractiveLaunchSpecServiceTests.cs

@@ -2,6 +2,7 @@ using ClaudeDo.Data.Git;
 using ClaudeDo.Data.Models;
 using ClaudeDo.Data.Repositories;
 using ClaudeDo.Worker.Config;
+using ClaudeDo.Worker.Planning;
 using ClaudeDo.Worker.Runner;
 using ClaudeDo.Worker.Skills;
 using ClaudeDo.Worker.Tests.Infrastructure;
@@ -342,4 +343,40 @@ public sealed class InteractiveLaunchSpecServiceTests : IDisposable
         await Assert.ThrowsAsync<InvalidOperationException>(
             () => svc.BuildForDirectoryAsync(Path.Combine(_tempDir, "does-not-exist"), CancellationToken.None));
     }
+
+    [Fact]
+    public void BuildPlanningStart_MapsPlanningArgsAndEnv()
+    {
+        var sessionDir = Path.Combine(_tempDir, "sess");
+        Directory.CreateDirectory(sessionDir);
+        var ctx = new PlanningSessionStartContext(
+            ParentTaskId: "p1", WorkingDir: _worktreeDir, Token: "tok-1",
+            WorktreePath: _worktreeDir, BranchName: "claudedo/planning/p1",
+            Files: new PlanningSessionFiles(sessionDir,
+                Path.Combine(sessionDir, "system-prompt.md"),
+                Path.Combine(sessionDir, "initial-prompt.txt")));
+
+        var spec = BuildService().BuildPlanningStart(ctx);
+
+        Assert.Equal(_worktreeDir, spec.Cwd);
+        Assert.Equal(_claudeStubPath, spec.Exe);
+        Assert.Contains("--permission-mode", spec.Args);
+        Assert.Contains("plan", spec.Args);
+        Assert.Equal("tok-1", spec.Env["CLAUDEDO_PLANNING_TOKEN"]);
+        Assert.Equal("20000", spec.Env["MAX_THINKING_TOKENS"]);
+    }
+
+    [Fact]
+    public void BuildPlanningResume_MapsResumeArgsAndToken()
+    {
+        var ctx = new PlanningSessionResumeContext(
+            ParentTaskId: "p1", WorkingDir: _worktreeDir,
+            ClaudeSessionId: "sess-42", Token: "tok-2", WorktreePath: _worktreeDir);
+
+        var spec = BuildService().BuildPlanningResume(ctx);
+
+        Assert.Equal(new[] { "--permission-mode", "plan", "--resume", "sess-42" }, spec.Args);
+        Assert.Equal("tok-2", spec.Env["CLAUDEDO_PLANNING_TOKEN"]);
+        Assert.Equal(_worktreeDir, spec.Cwd);
+    }
 }