feat(worker): add PlanningChainCoordinator for sequential subtask execution

Coordinates Waiting -> Queued transitions between sibling subtasks: when a child finishes Done, the next Waiting sibling is promoted to Queued. WorkerHub.QueuePlanningSubtasksAsync exposes this to the UI; TaskRunner advances the chain on completion. Also tightens the planning-session prompt: planner must use MCP tools, not direct edits.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/ClaudeDo.Worker.Tests/Planning/PlanningChainCoordinatorTests.cs

@@ -0,0 +1,164 @@
+using ClaudeDo.Data;
+using ClaudeDo.Data.Models;
+using ClaudeDo.Worker.Planning;
+using ClaudeDo.Worker.Tests.Infrastructure;
+using Microsoft.EntityFrameworkCore;
+using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
+
+namespace ClaudeDo.Worker.Tests.Planning;
+
+public sealed class PlanningChainCoordinatorTests : IDisposable
+{
+    private readonly DbFixture _db = new();
+    private readonly TestDbContextFactory _factory;
+    private readonly PlanningChainCoordinator _sut;
+    private readonly string _listId;
+
+    public PlanningChainCoordinatorTests()
+    {
+        _factory = _db.CreateFactory();
+        _sut = new PlanningChainCoordinator(_factory);
+        _listId = Guid.NewGuid().ToString();
+        using var ctx = _factory.CreateDbContext();
+        ctx.Lists.Add(new ListEntity
+        {
+            Id = _listId,
+            Name = "Test",
+            CreatedAt = DateTime.UtcNow,
+            DefaultCommitType = "chore",
+        });
+        ctx.SaveChanges();
+    }
+
+    public void Dispose() => _db.Dispose();
+
+    private async Task SeedPlanningFamilyAsync(string parentId, int childCount)
+    {
+        await using var ctx = _factory.CreateDbContext();
+        ctx.Tasks.Add(new TaskEntity
+        {
+            Id = parentId,
+            ListId = _listId,
+            Title = "Parent",
+            CreatedAt = DateTime.UtcNow,
+            Status = TaskStatus.Planned,
+        });
+        for (int i = 0; i < childCount; i++)
+        {
+            ctx.Tasks.Add(new TaskEntity
+            {
+                Id = $"{parentId}-c{i}",
+                ListId = _listId,
+                Title = $"Child {i}",
+                CreatedAt = DateTime.UtcNow,
+                Status = TaskStatus.Manual,
+                ParentTaskId = parentId,
+                SortOrder = i,
+            });
+        }
+        await ctx.SaveChangesAsync();
+    }
+
+    private async Task<List<TaskEntity>> GetChildrenAsync(string parentId)
+    {
+        await using var ctx = _factory.CreateDbContext();
+        return await ctx.Tasks
+            .AsNoTracking()
+            .Where(t => t.ParentTaskId == parentId)
+            .OrderBy(t => t.SortOrder)
+            .ToListAsync();
+    }
+
+    [Fact]
+    public async Task QueueSubtasksSequentially_SetsFirstQueued_RestWaiting()
+    {
+        await SeedPlanningFamilyAsync("P", 3);
+
+        await _sut.QueueSubtasksSequentiallyAsync("P", default);
+
+        var kids = await GetChildrenAsync("P");
+        Assert.Equal(TaskStatus.Queued, kids[0].Status);
+        Assert.Equal(TaskStatus.Waiting, kids[1].Status);
+        Assert.Equal(TaskStatus.Waiting, kids[2].Status);
+    }
+
+    [Fact]
+    public async Task OnChildDone_FlipsNextWaitingToQueued()
+    {
+        await SeedPlanningFamilyAsync("P", 3);
+        await _sut.QueueSubtasksSequentiallyAsync("P", default);
+
+        // Simulate first child finishing Done.
+        await using (var ctx = _factory.CreateDbContext())
+        {
+            var first = await ctx.Tasks.FirstAsync(t => t.Id == "P-c0");
+            first.Status = TaskStatus.Done;
+            await ctx.SaveChangesAsync();
+        }
+
+        var advanced = await _sut.OnChildFinishedAsync("P-c0", TaskStatus.Done, default);
+
+        Assert.Equal("P-c1", advanced);
+        var kids = await GetChildrenAsync("P");
+        Assert.Equal(TaskStatus.Done, kids[0].Status);
+        Assert.Equal(TaskStatus.Queued, kids[1].Status);
+        Assert.Equal(TaskStatus.Waiting, kids[2].Status);
+    }
+
+    [Fact]
+    public async Task OnChildFailed_DoesNotAdvanceChain()
+    {
+        await SeedPlanningFamilyAsync("P", 3);
+        await _sut.QueueSubtasksSequentiallyAsync("P", default);
+
+        await using (var ctx = _factory.CreateDbContext())
+        {
+            var first = await ctx.Tasks.FirstAsync(t => t.Id == "P-c0");
+            first.Status = TaskStatus.Failed;
+            await ctx.SaveChangesAsync();
+        }
+
+        var advanced = await _sut.OnChildFinishedAsync("P-c0", TaskStatus.Failed, default);
+
+        Assert.Null(advanced);
+        var kids = await GetChildrenAsync("P");
+        Assert.Equal(TaskStatus.Failed, kids[0].Status);
+        Assert.Equal(TaskStatus.Waiting, kids[1].Status);
+        Assert.Equal(TaskStatus.Waiting, kids[2].Status);
+    }
+
+    [Fact]
+    public async Task OnChildDone_LastChild_ReturnsNull()
+    {
+        await SeedPlanningFamilyAsync("P", 2);
+        await _sut.QueueSubtasksSequentiallyAsync("P", default);
+
+        // Mark both done, simulating chain reaching the end.
+        await using (var ctx = _factory.CreateDbContext())
+        {
+            foreach (var t in ctx.Tasks.Where(t => t.ParentTaskId == "P"))
+                t.Status = TaskStatus.Done;
+            await ctx.SaveChangesAsync();
+        }
+
+        var advanced = await _sut.OnChildFinishedAsync("P-c1", TaskStatus.Done, default);
+
+        Assert.Null(advanced);
+    }
+
+    [Fact]
+    public async Task QueueSubtasksSequentially_RejectsNonManualChildren()
+    {
+        await SeedPlanningFamilyAsync("P", 2);
+        // Corrupt one child to be already Queued.
+        await using (var ctx = _factory.CreateDbContext())
+        {
+            var first = await ctx.Tasks.FirstAsync(t => t.Id == "P-c0");
+            first.Status = TaskStatus.Queued;
+            await ctx.SaveChangesAsync();
+        }
+
+        await Assert.ThrowsAsync<InvalidOperationException>(
+            () => _sut.QueueSubtasksSequentiallyAsync("P", default));
+    }
+}