fix(worker): make list_tasks/batch_get_tasks lean by default

list_tasks on a list of ~100 verbosely-described tasks could return
390k+ characters in one call, blowing past the caller's token limit.
Both tools now default to lean TaskRefDto references (no
Description/Result) and take an includeDescription flag to opt back
into the full TaskDto payload — same flag-alongside-nullable-payload
idiom already used by BatchGetTaskResult/TaskConfigResult. get_task is
unchanged.

src/ClaudeDo.Worker/External/BatchMcpTools.cs

@@ -6,7 +6,10 @@ namespace ClaudeDo.Worker.External;
 public sealed record BatchAddTaskInput(string Title, string? Description = null, string? Model = null);
 public sealed record BatchSetMyDayInput(string TaskId, bool IsMyDay, int? SortOrder = null);
 
-public sealed record BatchGetTaskResult(string Id, bool Found, TaskDto? Task, string? Error);
+// task is populated when found and includeDescription=false (the default, lean reference);
+// taskFull is populated when found and includeDescription=true (full task incl.
+// Description/Result). Both are null when found=false.
+public sealed record BatchGetTaskResult(string Id, bool Found, TaskRefDto? Task, TaskDto? TaskFull, string? Error);
 public sealed record BatchAddTaskResult(int Index, string Title, bool Ok, TaskRefDto? Task, string? Error);
 public sealed record BatchTaskResult(string TaskId, bool Ok, string? Error);
 public sealed record BatchCancelResult(string TaskId, bool Ok, bool Cancelled, string? Error);
@@ -30,10 +33,13 @@ public sealed class BatchMcpTools
 
     [McpServerTool, Description(
         "Fetch a snapshot of many tasks in one call (overview / polling a fan-out). " +
-        "Returns one result per id: { id, found, task, error }. A missing id is found=false " +
-        "(not an error); error is only set for an unexpected failure. Max 100 ids.")]
+        "Returns one result per id: { id, found, task, taskFull, error }. " +
+        "includeDescription=false (default): found tasks come back in `task` (lean reference, no " +
+        "Description/Result). includeDescription=true: found tasks come back in `taskFull` (incl. " +
+        "Description/Result) instead. A missing id is found=false (not an error; task and taskFull both null); " +
+        "error is only set for an unexpected failure. Max 100 ids.")]
     public async Task<IReadOnlyList<BatchGetTaskResult>> BatchGetTasks(
-        string[] taskIds, CancellationToken cancellationToken)
+        string[] taskIds, bool includeDescription = false, CancellationToken cancellationToken = default)
     {
         EnsureWithinCap(taskIds, nameof(taskIds));
 
@@ -42,17 +48,25 @@ public sealed class BatchMcpTools
         {
             try
             {
-                var task = await _svc.GetTask(id, cancellationToken);
-                results.Add(new BatchGetTaskResult(id, true, task, null));
+                if (includeDescription)
+                {
+                    var task = await _svc.GetTask(id, cancellationToken);
+                    results.Add(new BatchGetTaskResult(id, true, null, task, null));
+                }
+                else
+                {
+                    var taskRef = await _svc.GetTaskRefAsync(id, cancellationToken);
+                    results.Add(new BatchGetTaskResult(id, true, taskRef, null, null));
+                }
             }
             catch (OperationCanceledException) { throw; }
             catch (InvalidOperationException)
             {
-                results.Add(new BatchGetTaskResult(id, false, null, null));
+                results.Add(new BatchGetTaskResult(id, false, null, null, null));
             }
             catch (Exception ex)
             {
-                results.Add(new BatchGetTaskResult(id, false, null, ex.Message));
+                results.Add(new BatchGetTaskResult(id, false, null, null, ex.Message));
             }
         }
         return results;

src/ClaudeDo.Worker/External/ExternalMcpService.cs

@@ -47,6 +47,15 @@ public sealed record TaskRefDto(
     int SortOrder,
     bool IsMyDay);
 
+// tasks is populated when includeDescription=false (the default): lean references, no
+// Description/Result. tasksFull is populated when includeDescription=true: full tasks incl.
+// Description/Result. Exactly one of the two is non-null per the includeDescription flag —
+// same "flag alongside nullable payload" idiom as BatchGetTaskResult.
+public sealed record ListTasksResult(
+    bool IncludeDescription,
+    IReadOnlyList<TaskRefDto>? Tasks,
+    IReadOnlyList<TaskDto>? TasksFull);
+
 public sealed record WorktreeInfoDto(
     string Path, string Branch, string HeadCommit, string BaseCommit,
     int Ahead, int Behind, bool IsDirty, string? MergeCommit = null);
@@ -139,11 +148,17 @@ public sealed class ExternalMcpService
 
     [McpServerTool, Description(
         "List tasks in a given list. Optionally filter by creator (createdBy) and/or status. " +
-        "Valid status values: Idle, Queued, Running, WaitingForReview, WaitingForChildren, Done, Failed, Cancelled.")]
-    public async Task<IReadOnlyList<TaskDto>> ListTasks(
+        "Valid status values: Idle, Queued, Running, WaitingForReview, WaitingForChildren, Done, Failed, Cancelled. " +
+        "includeDescription=false (default): returns lean task references in `tasks` (no Description/Result) — " +
+        "use this unless you actually need the description text, since a list of verbosely-described tasks can " +
+        "otherwise blow past the response size limit. " +
+        "includeDescription=true: returns full tasks (incl. Description/Result) in `tasksFull` instead; `tasks` is " +
+        "null in that case.")]
+    public async Task<ListTasksResult> ListTasks(
         string listId,
         string? createdBy = null,
         string? status = null,
+        bool includeDescription = false,
         CancellationToken cancellationToken = default)
     {
         TaskStatus? statusFilter = null;
@@ -162,7 +177,10 @@ public sealed class ExternalMcpService
         if (statusFilter is not null)
             query = query.Where(t => t.Status == statusFilter);
 
-        return query.Select(ToDto).ToList();
+        var filtered = query.ToList();
+        return includeDescription
+            ? new ListTasksResult(true, null, filtered.Select(ToDto).ToList())
+            : new ListTasksResult(false, filtered.Select(ToRefDto).ToList(), null);
     }
 
     [McpServerTool, Description(
@@ -177,6 +195,15 @@ public sealed class ExternalMcpService
         return ToDto(task);
     }
 
+    // Lean counterpart to GetTask, used internally by BatchGetTasks' default (includeDescription=false)
+    // path. Not an MCP tool itself — GetTask's own behavior stays untouched.
+    internal async Task<TaskRefDto> GetTaskRefAsync(string taskId, CancellationToken cancellationToken)
+    {
+        var task = await _tasks.GetByIdAsync(taskId, cancellationToken)
+            ?? throw new InvalidOperationException($"Task {taskId} not found.");
+        return ToRefDto(task);
+    }
+
     [McpServerTool, Description(
         "Create a new task in the given list. Set queueImmediately=true to enqueue it for agent execution. " +
         "Set model to the cheapest model that can do the task well — 'haiku' for trivial/mechanical work, " +