feat(daily-prep): add set_my_day MCP tool with cap-guard

src/ClaudeDo.Worker/External/ExternalMcpService.cs

@@ -30,7 +30,9 @@ public sealed record TaskDto(
     string? CreatedBy,
     DateTime CreatedAt,
     DateTime? StartedAt,
-    DateTime? FinishedAt);
+    DateTime? FinishedAt,
+    bool IsMyDay,
+    int SortOrder);
 
 public sealed record WorktreeInfoDto(
     string Path, string Branch, string HeadCommit, string BaseCommit,
@@ -529,6 +531,41 @@ public sealed class ExternalMcpService
         return new DailyPrepDataDto(maxTasks, candidates, currentMyDay);
     }
 
+    [McpServerTool, Description(
+        "Daily prep: set or clear a task's MyDay flag, optionally setting its sortOrder " +
+        "(use consecutive sortOrder values to keep related tasks together). " +
+        "Setting isMyDay=true is rejected if it would exceed the MyDay cap (DailyPrepMaxTasks open MyDay tasks); " +
+        "clearing (isMyDay=false) is always allowed.")]
+    public async Task<TaskDto> SetMyDay(
+        string taskId,
+        bool isMyDay,
+        int? sortOrder,
+        CancellationToken cancellationToken)
+    {
+        await using var ctx = await _dbFactory.CreateDbContextAsync(cancellationToken);
+
+        var task = await ctx.Tasks.FirstOrDefaultAsync(t => t.Id == taskId, cancellationToken)
+            ?? throw new InvalidOperationException($"Task {taskId} not found.");
+
+        if (isMyDay && !task.IsMyDay)
+        {
+            var settings = await new AppSettingsRepository(ctx).GetAsync(cancellationToken);
+            var max = settings.DailyPrepMaxTasks < 1 ? 1 : settings.DailyPrepMaxTasks;
+            var openMyDay = await ctx.Tasks.CountAsync(
+                t => t.IsMyDay && t.Status == TaskStatus.Idle, cancellationToken);
+            if (openMyDay >= max)
+                throw new InvalidOperationException(
+                    $"MyDay limit {max} reached. Clear a task before adding another.");
+        }
+
+        task.IsMyDay = isMyDay;
+        if (sortOrder is not null) task.SortOrder = sortOrder.Value;
+        await ctx.SaveChangesAsync(cancellationToken);
+
+        await _broadcaster.TaskUpdated(taskId);
+        return ToDto(task);
+    }
+
     private static DailyPrepCandidateDto ToCandidate(TaskEntity t) => new(
         t.Id, t.ListId, t.List?.Name ?? "", t.Title, t.Description,
         t.IsStarred, t.ScheduledFor, t.CreatedAt);
@@ -618,7 +655,9 @@ public sealed class ExternalMcpService
         t.CreatedBy,
         t.CreatedAt,
         t.StartedAt,
-        t.FinishedAt);
+        t.FinishedAt,
+        t.IsMyDay,
+        t.SortOrder);
 }
 
 internal static class DailyPrepFilter