feat(interactive): seed fresh task session with the task prompt

A fresh (non-resume) task-based ConPTY session now opens claude on the task's
prompt (title + description) as the positional argument, so the session starts on
the task instead of an empty prompt. Resume sessions and ad-hoc sessions are
unchanged.

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

@@ -181,7 +181,7 @@ public sealed class InteractiveLaunchSpecServiceTests : IDisposable
         Assert.True(Directory.Exists(wtRow.Path));
 
         Assert.Equal(wtRow.Path, spec.Cwd);
-        Assert.Empty(spec.Args);
+        Assert.Equal(new[] { "T" }, spec.Args); // fresh session seeds the task title as the prompt
         Assert.Equal(_claudeStubPath, spec.Exe);
     }
 
@@ -258,7 +258,7 @@ public sealed class InteractiveLaunchSpecServiceTests : IDisposable
         var svc = BuildService();
         var spec = await svc.BuildForTaskAsync(taskId, CancellationToken.None);
 
-        Assert.Empty(spec.Args);
+        Assert.Equal(new[] { "T" }, spec.Args); // fresh: seeds the task title as the prompt
         Assert.Equal(_worktreeDir, spec.Cwd);
     }
 
@@ -274,7 +274,27 @@ public sealed class InteractiveLaunchSpecServiceTests : IDisposable
         var svc = BuildService();
         var spec = await svc.BuildForTaskAsync(taskId, CancellationToken.None);
 
-        Assert.Empty(spec.Args);
+        Assert.Equal(new[] { "T" }, spec.Args); // fresh: seeds the task title as the prompt
+    }
+
+    [Fact]
+    public async Task BuildForTaskAsync_FreshTask_WithDescription_SeedsTitleAndDescriptionPrompt()
+    {
+        var listId = await SeedListAsync();
+        var taskId = Guid.NewGuid().ToString();
+        await SeedTaskAsync(taskId, listId, TaskStatus.Idle);
+        await SeedWorktreeAsync(taskId, WorktreeState.Active);
+        using (var ctx = _db.CreateContext())
+        {
+            var t = await ctx.Tasks.FindAsync(taskId);
+            t!.Description = "Do the thing";
+            await ctx.SaveChangesAsync();
+        }
+
+        var svc = BuildService();
+        var spec = await svc.BuildForTaskAsync(taskId, CancellationToken.None);
+
+        Assert.Equal(new[] { "T\n\nDo the thing" }, spec.Args);
     }
 
     [Fact]