refactor(ui): unify list-linked-repo predicate into RepoLinkage

ListsIslandViewModel and SettingsModalViewModel each re-implemented "does
this list have a linked WorkingDir" with different whitespace handling.
RepoLinkage.IsLinked/IsLinkedInDb is now the single definition; both
callers derive from it, closing the whitespace-only WorkingDir gap where
the Settings modal disagreed with the ListsIsland banner.

src/ClaudeDo.Ui/Services/RepoLinkage.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Linq.Expressions;
+using ClaudeDo.Data.Models;
+
+namespace ClaudeDo.Ui.Services;
+
+// Single definition of "does this list have a linked repo" — a WorkingDir that is set to
+// something other than blank/whitespace. ListsIslandViewModel and SettingsModalViewModel each
+// answer this over a different scope (UserLists in memory vs. all Lists rows in the DB) and need
+// it in different shapes, but both must agree on what "linked" means.
+public static class RepoLinkage
+{
+    public static bool IsLinked(string? workingDir) => !string.IsNullOrWhiteSpace(workingDir);
+
+    // EF Core can't translate string.IsNullOrWhiteSpace against Sqlite, so the DB-side check is
+    // spelled out via Trim() instead — same semantics as IsLinked above.
+    public static readonly Expression<Func<ListEntity, bool>> IsLinkedInDb =
+        l => l.WorkingDir != null && l.WorkingDir.Trim() != "";
+}

src/ClaudeDo.Ui/ViewModels/Islands/ListsIslandViewModel.cs

@@ -187,12 +187,14 @@ public sealed partial class ListsIslandViewModel : ViewModelBase, IDisposable
     [ObservableProperty] private ListNavItemViewModel? _selectedList;
 
     /// <summary>True whenever no User list has a linked <c>WorkingDir</c> — drives the no-repo
-    /// banner. Smart/Virtual lists never count. Recomputed after every load and every
+    /// banner. Smart/Virtual lists never count (scope intentionally narrower than
-    /// list CRUD / list-settings save; never persisted, no dismiss state.</summary>
+    /// SettingsModalViewModel.HasLinkedRepo, which checks all Lists rows in the DB). Recomputed
+    /// after every load and every list CRUD / list-settings save; never persisted, no dismiss
+    /// state.</summary>
     [ObservableProperty] private bool _hasNoLinkedRepo = true;
 
     private void RecomputeHasNoLinkedRepo() =>
-        HasNoLinkedRepo = UserLists.All(r => string.IsNullOrWhiteSpace(r.WorkingDir));
+        HasNoLinkedRepo = UserLists.All(r => !RepoLinkage.IsLinked(r.WorkingDir));
 
     public string UserName { get; } = Environment.UserName;
     public string MachineName { get; } = Environment.MachineName;

src/ClaudeDo.Ui/ViewModels/Modals/SettingsModalViewModel.cs

@@ -56,6 +56,8 @@ public sealed partial class SettingsModalViewModel : ViewModelBase
 
     // True once at least one list has a linked repo (WorkingDir). Drives the repo-hint strip on
     // Worktrees/Prime Claude/Session Skills/Berichte — nothing is ever hidden, just annotated.
+    // Scope intentionally broader than ListsIslandViewModel.HasNoLinkedRepo (all Lists rows in
+    // the DB, not just UserLists).
     [ObservableProperty] private bool _hasLinkedRepo;
 
     // Wired by WindowDialogService to close this modal and open the existing repo-import flow.
@@ -152,7 +154,7 @@ public sealed partial class SettingsModalViewModel : ViewModelBase
             General.LoadModelPresets(dto?.ModelPresets, General.MaxTurnsCeiling);
 
             await using var ctx = await _dbFactory.CreateDbContextAsync();
-            HasLinkedRepo = await ctx.Lists.AnyAsync(l => l.WorkingDir != null && l.WorkingDir != "");
+            HasLinkedRepo = await ctx.Lists.AnyAsync(RepoLinkage.IsLinkedInDb);
         }
         finally { IsBusy = false; }
     }

tests/ClaudeDo.Ui.Tests/ViewModels/SettingsModalViewModelTests.cs

@@ -167,6 +167,21 @@ public class SettingsModalViewModelTests : IDisposable
         Assert.True(vm.HasLinkedRepo);
     }
 
+    [Fact]
+    public async Task HasLinkedRepo_false_when_a_list_working_dir_is_whitespace_only()
+    {
+        using (var ctx = NewContext())
+        {
+            ctx.Lists.Add(new ListEntity { Id = "l1", Name = "Blank repo", CreatedAt = DateTime.UtcNow, WorkingDir = "   " });
+            ctx.SaveChanges();
+        }
+        var vm = MakeVm(new FakeWorker());
+
+        await vm.LoadAsync();
+
+        Assert.False(vm.HasLinkedRepo);
+    }
+
     [Fact]
     public void SelectedCategory_updates_SelectedIndex_and_ignores_null()
     {