fix(worker-client): stop swallowing mutating hub call failures

TryInvokeAsync catches every exception and returns null, which is fine
for read-only calls but hid real HubException reasons behind a generic
"offline" message for the 7 mutating call sites (RestoreDefaultAgents,
UpsertPrimeSchedule, AddDailyNote, CleanupFinishedWorktrees,
ResetAllWorktrees, ForceRemoveWorktree, BuildPlanningIntegrationBranch)
— the same bug class fixed for ApproveReview in e1807fd. Each of the 22
TryInvokeAsync call sites was audited; the 15 read-only ones are left
unchanged (empty/offline is the right display). For the 7 switched to
a direct hub invoke, every caller was checked and, where it had no
catch, one was added so the exception surfaces (StatusMessage,
ShowErrorAsync/CombinedWarning) instead of crashing.

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

@@ -19,6 +19,14 @@ public class PrimeClaudeTabViewModelTests
         public Task DeleteAsync(Guid id) { Deletes.Add(id); return Task.CompletedTask; }
     }
 
+    private sealed class ThrowingApi : IPrimeScheduleApi
+    {
+        public string ExceptionMessage { get; init; } = "worker offline";
+        public Task<List<PrimeScheduleDto>> ListAsync() => Task.FromResult(new List<PrimeScheduleDto>());
+        public Task<PrimeScheduleDto?> UpsertAsync(PrimeScheduleDto dto) => throw new Exception(ExceptionMessage);
+        public Task DeleteAsync(Guid id) => Task.CompletedTask;
+    }
+
     private static PrimeScheduleDto Dto(Guid id, int days, TimeSpan time) =>
         new(id, days, time, true, null, null);
 
@@ -93,4 +101,19 @@ public class PrimeClaudeTabViewModelTests
         vm.AddScheduleCommand.Execute(null);
         Assert.Null(vm.Validate());
     }
+
+    // SettingsModalViewModel.Save() is the only place that catches Prime.SaveAsync's
+    // failures (via a try/catch around the whole settings save) and surfaces them as
+    // "Save failed: {message}". For that to work, SaveAsync must propagate the worker's
+    // exception rather than swallow it.
+    [Fact]
+    public async Task Save_WhenApiThrows_PropagatesException()
+    {
+        var api = new ThrowingApi();
+        var vm = new PrimeClaudeTabViewModel(api);
+        vm.AddScheduleCommand.Execute(null);
+
+        var ex = await Assert.ThrowsAsync<Exception>(() => vm.SaveAsync());
+        Assert.Equal(api.ExceptionMessage, ex.Message);
+    }
 }