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.Worker/Runner/InteractiveLaunchSpecService.cs

@@ -107,6 +107,40 @@ public sealed class InteractiveLaunchSpecService : IInteractiveLaunchSpecService
         return new LaunchSpec(worktree.Path, resolvedClaude, args, env);
     }
 
+    public LaunchSpec BuildPlanningStart(PlanningSessionStartContext ctx)
+    {
+        var resolvedClaude = WindowsTerminalLauncher.Resolve(_claudePath)
+            ?? throw new InvalidOperationException($"claude executable not found: {_claudePath}");
+
+        // Mirrors the env the wt planning launcher set (MAX_THINKING_TOKENS + the per-session
+        // planning token); MCP_TOOL_TIMEOUT matches the other embedded-ConPTY specs. Applied to
+        // the UI process env at spawn time (see PtyTerminalSession) — process-global by design.
+        var env = new Dictionary<string, string>
+        {
+            ["MAX_THINKING_TOKENS"] = "20000",
+            ["CLAUDEDO_PLANNING_TOKEN"] = ctx.Token,
+            ["MCP_TOOL_TIMEOUT"] = "200000",
+        };
+
+        return new LaunchSpec(
+            ctx.WorkingDir, resolvedClaude, WindowsTerminalLauncher.BuildPlanningStartArgs(ctx), env);
+    }
+
+    public LaunchSpec BuildPlanningResume(PlanningSessionResumeContext ctx)
+    {
+        var resolvedClaude = WindowsTerminalLauncher.Resolve(_claudePath)
+            ?? throw new InvalidOperationException($"claude executable not found: {_claudePath}");
+
+        var env = new Dictionary<string, string>
+        {
+            ["CLAUDEDO_PLANNING_TOKEN"] = ctx.Token,
+            ["MCP_TOOL_TIMEOUT"] = "200000",
+        };
+
+        return new LaunchSpec(
+            ctx.WorkingDir, resolvedClaude, WindowsTerminalLauncher.BuildPlanningResumeArgs(ctx.ClaudeSessionId), env);
+    }
+
     public Task<LaunchSpec> BuildForDirectoryAsync(string directory, CancellationToken ct)
     {
         if (!Directory.Exists(directory))