feat(worker): PlanningSessionManager.StartAsync

Add PlanningSessionFiles, PlanningSessionStartContext/ResumeContext DTOs,
PlanningSessionManager.StartAsync (file scaffolding + status transition),
and integration tests. Also fix migration discovery by adding [DbContext]
attribute to all migration classes and switch DbFixture to EnsureCreated.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ClaudeDo.Data/Migrations/20260416064948_InitialCreate.cs

@@ -1,4 +1,6 @@
 using System;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Migrations;
 
 #nullable disable
@@ -8,6 +10,8 @@ using Microsoft.EntityFrameworkCore.Migrations;
 namespace ClaudeDo.Data.Migrations
 {
     /// <inheritdoc />
+    [DbContext(typeof(ClaudeDoDbContext))]
+    [Migration("20260416064948_InitialCreate")]
     public partial class InitialCreate : Migration
     {
         /// <inheritdoc />

src/ClaudeDo.Data/Migrations/20260420075929_AddTaskFlagsAndNotes.cs

@@ -1,10 +1,14 @@
-using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
 
 #nullable disable
 
 namespace ClaudeDo.Data.Migrations
 {
     /// <inheritdoc />
+    [DbContext(typeof(ClaudeDoDbContext))]
+    [Migration("20260420075929_AddTaskFlagsAndNotes")]
     public partial class AddTaskFlagsAndNotes : Migration
     {
         /// <inheritdoc />

src/ClaudeDo.Data/Migrations/20260421113614_AddAppSettings.cs

@@ -1,10 +1,14 @@
-using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
 
 #nullable disable
 
 namespace ClaudeDo.Data.Migrations
 {
     /// <inheritdoc />
+    [DbContext(typeof(ClaudeDoDbContext))]
+    [Migration("20260421113614_AddAppSettings")]
     public partial class AddAppSettings : Migration
     {
         /// <inheritdoc />

src/ClaudeDo.Data/Migrations/20260422120000_AddTaskSortOrder.cs

@@ -1,3 +1,5 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Migrations;
 
 #nullable disable
@@ -5,6 +7,8 @@ using Microsoft.EntityFrameworkCore.Migrations;
 namespace ClaudeDo.Data.Migrations
 {
     /// <inheritdoc />
+    [DbContext(typeof(ClaudeDoDbContext))]
+    [Migration("20260422120000_AddTaskSortOrder")]
     public partial class AddTaskSortOrder : Migration
     {
         /// <inheritdoc />

src/ClaudeDo.Data/Migrations/20260423154708_AddPlanningSupport.cs

@@ -1,4 +1,6 @@
 using System;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Migrations;
 
 #nullable disable
@@ -6,6 +8,8 @@ using Microsoft.EntityFrameworkCore.Migrations;
 namespace ClaudeDo.Data.Migrations
 {
     /// <inheritdoc />
+    [DbContext(typeof(ClaudeDoDbContext))]
+    [Migration("20260423154708_AddPlanningSupport")]
     public partial class AddPlanningSupport : Migration
     {
         /// <inheritdoc />

src/ClaudeDo.Worker/Planning/PlanningSessionContext.cs

@@ -0,0 +1,12 @@
+namespace ClaudeDo.Worker.Planning;
+
+public sealed record PlanningSessionStartContext(
+    string ParentTaskId,
+    string WorkingDir,
+    PlanningSessionFiles Files);
+
+public sealed record PlanningSessionResumeContext(
+    string ParentTaskId,
+    string WorkingDir,
+    string ClaudeSessionId,
+    string McpConfigPath);

src/ClaudeDo.Worker/Planning/PlanningSessionFiles.cs

@@ -0,0 +1,7 @@
+namespace ClaudeDo.Worker.Planning;
+
+public sealed record PlanningSessionFiles(
+    string SessionDirectory,
+    string McpConfigPath,
+    string SystemPromptPath,
+    string InitialPromptPath);

src/ClaudeDo.Worker/Planning/PlanningSessionManager.cs

@@ -0,0 +1,111 @@
+using System.Security.Cryptography;
+using System.Text;
+using System.Text.Json;
+using ClaudeDo.Data.Models;
+using ClaudeDo.Data.Repositories;
+using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
+
+namespace ClaudeDo.Worker.Planning;
+
+public sealed class PlanningSessionManager
+{
+    private const string McpServerUrl = "http://127.0.0.1:47821/mcp";
+
+    private readonly TaskRepository _tasks;
+    private readonly ListRepository _lists;
+    private readonly string _rootDirectory;
+
+    public PlanningSessionManager(TaskRepository tasks, ListRepository lists, string rootDirectory)
+    {
+        _tasks = tasks;
+        _lists = lists;
+        _rootDirectory = rootDirectory;
+    }
+
+    public async Task<PlanningSessionStartContext> StartAsync(string taskId, CancellationToken ct)
+    {
+        var task = await _tasks.GetByIdAsync(taskId, ct)
+            ?? throw new InvalidOperationException($"Task {taskId} not found.");
+        if (task.ParentTaskId is not null)
+            throw new InvalidOperationException("Cannot start a planning session on a child task.");
+        if (task.Status != TaskStatus.Manual)
+            throw new InvalidOperationException($"Task is in status {task.Status}; only Manual can start planning.");
+
+        var token = GenerateToken();
+        _ = await _tasks.SetPlanningStartedAsync(taskId, token, ct)
+            ?? throw new InvalidOperationException("Failed to transition task to Planning.");
+
+        var sessionDir = Path.Combine(_rootDirectory, taskId);
+        Directory.CreateDirectory(sessionDir);
+
+        var files = new PlanningSessionFiles(
+            sessionDir,
+            Path.Combine(sessionDir, "mcp.json"),
+            Path.Combine(sessionDir, "system-prompt.md"),
+            Path.Combine(sessionDir, "initial-prompt.txt"));
+
+        await File.WriteAllTextAsync(files.McpConfigPath, BuildMcpConfigJson(token), ct);
+        await File.WriteAllTextAsync(files.SystemPromptPath, BuildSystemPrompt(), ct);
+        await File.WriteAllTextAsync(files.InitialPromptPath, BuildInitialPrompt(task), ct);
+
+        var list = await _lists.GetByIdAsync(task.ListId, ct)
+            ?? throw new InvalidOperationException($"List {task.ListId} not found.");
+        return new PlanningSessionStartContext(taskId, list.WorkingDir, files);
+    }
+
+    private static string GenerateToken()
+    {
+        var bytes = RandomNumberGenerator.GetBytes(32);
+        return Convert.ToBase64String(bytes)
+            .Replace('+', '-')
+            .Replace('/', '_')
+            .TrimEnd('=');
+    }
+
+    private static string BuildMcpConfigJson(string token)
+    {
+        var payload = new
+        {
+            mcpServers = new
+            {
+                claudedo = new
+                {
+                    type = "http",
+                    url = McpServerUrl,
+                    headers = new Dictionary<string, string>
+                    {
+                        ["Authorization"] = $"Bearer {token}"
+                    }
+                }
+            }
+        };
+        return JsonSerializer.Serialize(payload, new JsonSerializerOptions { WriteIndented = true });
+    }
+
+    private static string BuildSystemPrompt() =>
+        """
+        You are a planning assistant for ClaudeDo.
+        Your role is to help break down a task into smaller, actionable subtasks.
+
+        Use the available MCP tools (mcp__claudedo__*) to create child tasks.
+        When you are done planning, finalize the session.
+
+        Be concise and focused. Each subtask should be independently executable.
+        """;
+
+    private static string BuildInitialPrompt(TaskEntity task)
+    {
+        var sb = new StringBuilder();
+        sb.AppendLine($"# Task: {task.Title}");
+        if (!string.IsNullOrWhiteSpace(task.Description))
+        {
+            sb.AppendLine();
+            sb.AppendLine(task.Description);
+        }
+        sb.AppendLine();
+        sb.AppendLine("---");
+        sb.AppendLine();
+        sb.AppendLine("Please analyze this task and break it down into concrete subtasks.");
+        return sb.ToString();
+    }
+}