feat(data): list_folders table plus lists.folder_id

Sidebar folders get their own table rather than a flag on lists, so the
places that enumerate lists (MCP tools, move-to-list, queue picker, repo
import) need no folder filtering. ON DELETE SET NULL keeps a folder's
lists alive when the folder goes.

src/ClaudeDo.Data/ClaudeDoDbContext.cs

@@ -43,6 +43,7 @@ public class ClaudeDoDbContext : DbContext
     public DbSet<TaskEntity> Tasks => Set<TaskEntity>();
     public DbSet<TaskDependencyEntity> TaskDependencies => Set<TaskDependencyEntity>();
     public DbSet<ListEntity> Lists => Set<ListEntity>();
+    public DbSet<ListFolderEntity> ListFolders => Set<ListFolderEntity>();
     public DbSet<ListConfigEntity> ListConfigs => Set<ListConfigEntity>();
     public DbSet<WorktreeEntity> Worktrees => Set<WorktreeEntity>();
     public DbSet<TaskRunEntity> TaskRuns => Set<TaskRunEntity>();

src/ClaudeDo.Data/Configuration/ListEntityConfiguration.cs

@@ -20,8 +20,17 @@ public class ListEntityConfiguration : IEntityTypeConfiguration<ListEntity>
         builder.Property(l => l.IsManual).HasColumnName("is_manual").IsRequired().HasDefaultValue(false);
         builder.Property(l => l.FindingsTracked).HasColumnName("findings_tracked").IsRequired().HasDefaultValue(false);
         builder.Property(l => l.Icon).HasColumnName("icon");
+        builder.Property(l => l.FolderId).HasColumnName("folder_id");
 
         builder.HasIndex(l => l.SortOrder).HasDatabaseName("idx_lists_sort");
+        builder.HasIndex(l => l.FolderId).HasDatabaseName("idx_lists_folder");
+
+        // No navigation property on either side: nothing needs the graph, and a nav would have to
+        // be Include'd (or silently come back empty) in every list query.
+        builder.HasOne<ListFolderEntity>()
+            .WithMany()
+            .HasForeignKey(l => l.FolderId)
+            .OnDelete(DeleteBehavior.SetNull);
 
         builder.HasOne(l => l.Config)
             .WithOne(c => c.List)

src/ClaudeDo.Data/Configuration/ListFolderEntityConfiguration.cs

@@ -0,0 +1,23 @@
+using ClaudeDo.Data.Models;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ClaudeDo.Data.Configuration;
+
+public class ListFolderEntityConfiguration : IEntityTypeConfiguration<ListFolderEntity>
+{
+    public void Configure(EntityTypeBuilder<ListFolderEntity> builder)
+    {
+        builder.ToTable("list_folders");
+
+        builder.HasKey(f => f.Id);
+        builder.Property(f => f.Id).HasColumnName("id");
+        builder.Property(f => f.Name).HasColumnName("name").IsRequired();
+        builder.Property(f => f.CreatedAt).HasColumnName("created_at").IsRequired();
+        builder.Property(f => f.Icon).HasColumnName("icon");
+        builder.Property(f => f.SortOrder).HasColumnName("sort_order").IsRequired().HasDefaultValue(0);
+        builder.Property(f => f.IsCollapsed).HasColumnName("is_collapsed").IsRequired().HasDefaultValue(false);
+
+        builder.HasIndex(f => f.SortOrder).HasDatabaseName("idx_list_folders_sort");
+    }
+}

src/ClaudeDo.Data/Migrations/20260910062251_AddListFolders.cs

@@ -0,0 +1,74 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ClaudeDo.Data.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddListFolders : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<string>(
+                name: "folder_id",
+                table: "lists",
+                type: "TEXT",
+                nullable: true);
+
+            migrationBuilder.CreateTable(
+                name: "list_folders",
+                columns: table => new
+                {
+                    id = table.Column<string>(type: "TEXT", nullable: false),
+                    name = table.Column<string>(type: "TEXT", nullable: false),
+                    created_at = table.Column<DateTime>(type: "TEXT", nullable: false),
+                    icon = table.Column<string>(type: "TEXT", nullable: true),
+                    sort_order = table.Column<int>(type: "INTEGER", nullable: false, defaultValue: 0),
+                    is_collapsed = table.Column<bool>(type: "INTEGER", nullable: false, defaultValue: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_list_folders", x => x.id);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "idx_lists_folder",
+                table: "lists",
+                column: "folder_id");
+
+            migrationBuilder.CreateIndex(
+                name: "idx_list_folders_sort",
+                table: "list_folders",
+                column: "sort_order");
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_lists_list_folders_folder_id",
+                table: "lists",
+                column: "folder_id",
+                principalTable: "list_folders",
+                principalColumn: "id",
+                onDelete: ReferentialAction.SetNull);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_lists_list_folders_folder_id",
+                table: "lists");
+
+            migrationBuilder.DropTable(
+                name: "list_folders");
+
+            migrationBuilder.DropIndex(
+                name: "idx_lists_folder",
+                table: "lists");
+
+            migrationBuilder.DropColumn(
+                name: "folder_id",
+                table: "lists");
+        }
+    }
+}

src/ClaudeDo.Data/Migrations/ClaudeDoDbContextModelSnapshot.cs

@@ -324,6 +324,10 @@ namespace ClaudeDo.Data.Migrations
                         .HasDefaultValue(false)
                         .HasColumnName("findings_tracked");
 
+                    b.Property<string>("FolderId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("folder_id");
+
                     b.Property<string>("Icon")
                         .HasColumnType("TEXT")
                         .HasColumnName("icon");
@@ -351,12 +355,54 @@ namespace ClaudeDo.Data.Migrations
 
                     b.HasKey("Id");
 
+                    b.HasIndex("FolderId")
+                        .HasDatabaseName("idx_lists_folder");
+
                     b.HasIndex("SortOrder")
                         .HasDatabaseName("idx_lists_sort");
 
                     b.ToTable("lists", (string)null);
                 });
 
+            modelBuilder.Entity("ClaudeDo.Data.Models.ListFolderEntity", b =>
+                {
+                    b.Property<string>("Id")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("Icon")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("icon");
+
+                    b.Property<bool>("IsCollapsed")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER")
+                        .HasDefaultValue(false)
+                        .HasColumnName("is_collapsed");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("name");
+
+                    b.Property<int>("SortOrder")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER")
+                        .HasDefaultValue(0)
+                        .HasColumnName("sort_order");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("SortOrder")
+                        .HasDatabaseName("idx_list_folders_sort");
+
+                    b.ToTable("list_folders", (string)null);
+                });
+
             modelBuilder.Entity("ClaudeDo.Data.Models.PrimeScheduleEntity", b =>
                 {
                     b.Property<Guid>("Id")
@@ -934,6 +980,14 @@ namespace ClaudeDo.Data.Migrations
                     b.Navigation("List");
                 });
 
+            modelBuilder.Entity("ClaudeDo.Data.Models.ListEntity", b =>
+                {
+                    b.HasOne("ClaudeDo.Data.Models.ListFolderEntity", null)
+                        .WithMany()
+                        .HasForeignKey("FolderId")
+                        .OnDelete(DeleteBehavior.SetNull);
+                });
+
             modelBuilder.Entity("ClaudeDo.Data.Models.SubtaskEntity", b =>
                 {
                     b.HasOne("ClaudeDo.Data.Models.TaskEntity", "Task")

src/ClaudeDo.Data/Models/ListEntity.cs

@@ -16,6 +16,9 @@ public sealed class ListEntity
     public bool FindingsTracked { get; set; }
     // Icon key into the UI's icon library (e.g. "Star"); null = the default folder icon.
     public string? Icon { get; set; }
+    // Sidebar folder this list sits in (ListFolderEntity.Id); null = top level. ON DELETE SET NULL,
+    // so deleting a folder moves its lists back to the top level instead of deleting them.
+    public string? FolderId { get; set; }
 
     // Navigation properties
     public ListConfigEntity? Config { get; set; }

src/ClaudeDo.Data/Models/ListFolderEntity.cs

@@ -0,0 +1,20 @@
+namespace ClaudeDo.Data.Models;
+
+/// <summary>
+/// A sidebar folder grouping user lists. Deliberately its own table rather than a flag on
+/// <see cref="ListEntity"/>: every place that enumerates lists (MCP list_task_lists, "move to
+/// list", the queue picker, repo import) would otherwise have to filter folders out.
+/// One level only — a folder holds lists, never other folders.
+/// </summary>
+public sealed class ListFolderEntity
+{
+    public required string Id { get; init; }
+    public required string Name { get; set; }
+    public required DateTime CreatedAt { get; init; }
+    // Icon key into the UI's icon library, same set as ListEntity.Icon; null = default folder icon.
+    public string? Icon { get; set; }
+    public int SortOrder { get; set; }
+    // Sidebar expand/collapse state. Lives here rather than in ui.config.json because the row is
+    // already being read for the folder itself.
+    public bool IsCollapsed { get; set; }
+}

src/ClaudeDo.Data/Repositories/ListRepository.cs

@@ -68,6 +68,58 @@ public sealed class ListRepository
         await _context.SaveChangesAsync(ct);
     }
 
+    // ---- Sidebar folders (list_folders) ----
+    // Folders live here rather than in their own repository because they exist only as a grouping
+    // of these lists — every caller that touches one already holds a ListRepository.
+
+    public async Task<List<ListFolderEntity>> GetFoldersAsync(CancellationToken ct = default)
+    {
+        return await _context.ListFolders
+            .OrderBy(f => f.SortOrder).ThenBy(f => f.CreatedAt)
+            .ToListAsync(ct);
+    }
+
+    public async Task AddFolderAsync(ListFolderEntity folder, CancellationToken ct = default)
+    {
+        folder.SortOrder = await _context.ListFolders.CountAsync(ct);
+        _context.ListFolders.Add(folder);
+        await _context.SaveChangesAsync(ct);
+    }
+
+    /// <summary>Patches just the two editable fields — a whole-entity Update would need
+    /// <c>CreatedAt</c>/<c>SortOrder</c>/<c>IsCollapsed</c> carried along and silently reset
+    /// whichever the caller forgot (see the SetConfigAsync note in CLAUDE.md).</summary>
+    public async Task RenameFolderAsync(string folderId, string name, string? icon, CancellationToken ct = default)
+    {
+        await _context.ListFolders
+            .Where(f => f.Id == folderId)
+            .ExecuteUpdateAsync(s => s
+                .SetProperty(f => f.Name, name)
+                .SetProperty(f => f.Icon, icon), ct);
+    }
+
+    /// <summary>Deletes the folder only — its lists survive and fall back to the top level via
+    /// the ON DELETE SET NULL on <c>lists.folder_id</c>.</summary>
+    public async Task DeleteFolderAsync(string folderId, CancellationToken ct = default)
+    {
+        await _context.ListFolders.Where(f => f.Id == folderId).ExecuteDeleteAsync(ct);
+    }
+
+    public async Task SetFolderCollapsedAsync(string folderId, bool collapsed, CancellationToken ct = default)
+    {
+        await _context.ListFolders
+            .Where(f => f.Id == folderId)
+            .ExecuteUpdateAsync(s => s.SetProperty(f => f.IsCollapsed, collapsed), ct);
+    }
+
+    /// <summary>Moves a list into <paramref name="folderId"/>, or back to the top level when null.</summary>
+    public async Task SetListFolderAsync(string listId, string? folderId, CancellationToken ct = default)
+    {
+        await _context.Lists
+            .Where(l => l.Id == listId)
+            .ExecuteUpdateAsync(s => s.SetProperty(l => l.FolderId, folderId), ct);
+    }
+
     public async Task<ListConfigEntity?> GetConfigAsync(string listId, CancellationToken ct = default)
     {
         return await _context.ListConfigs.FirstOrDefaultAsync(c => c.ListId == listId, ct);