feat(ui): add usage pill to footer and mission control header

Adds the IWorkerClient/WorkerClient usage surface (GetUsageSnapshot,
GetModelUsage, GetTaskUsage, UsageUpdated event) and a shared
UsagePillViewModel hosted once in IslandsShellViewModel (footer) and
once in MissionControlViewModel (header), showing "5h X% · 7d Y%"
with warn/blocked/stale states via existing design tokens. The
OpenMonitorCommand is wired but currently a no-op, pending the usage
monitor modal.

tests/ClaudeDo.Ui.Tests/StubWorkerClient.cs

@@ -36,6 +36,7 @@ public abstract class StubWorkerClient : IWorkerClient
     public event Action<string>? PlanningMergeAbortedEvent;
     public event Action<string>? PlanningCompletedEvent;
     public event Action<PrimeFiredEvent>? PrimeFired;
+    public event Action<UsageSnapshotDto>? UsageUpdatedEvent;
 #pragma warning restore CS0067
 
     public int ClearMyDayCalls { get; private set; }
@@ -151,5 +152,12 @@ public abstract class StubWorkerClient : IWorkerClient
     public virtual Task SetOnlineInboxAuthAsync(string refreshToken) => Task.CompletedTask;
     public virtual Task ClearOnlineInboxAuthAsync() => Task.CompletedTask;
 
+    public virtual Task<UsageSnapshotDto?> GetUsageSnapshotAsync() => Task.FromResult<UsageSnapshotDto?>(null);
+    public virtual Task<IReadOnlyList<ModelUsageRowDto>> GetModelUsageAsync(DateOnly from, DateOnly to)
+        => Task.FromResult<IReadOnlyList<ModelUsageRowDto>>(Array.Empty<ModelUsageRowDto>());
+    public virtual Task<IReadOnlyList<TaskUsageRowDto>> GetTaskUsageAsync(DateOnly from, DateOnly to)
+        => Task.FromResult<IReadOnlyList<TaskUsageRowDto>>(Array.Empty<TaskUsageRowDto>());
+    public void RaiseUsageUpdated(UsageSnapshotDto snapshot) => UsageUpdatedEvent?.Invoke(snapshot);
+
     protected void RaisePropertyChanged(string name) => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
 }

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

@@ -45,7 +45,7 @@ public class MissionControlViewModelTests : IDisposable
     private sealed class FakeWorker : StubWorkerClient { }
 
     private MissionControlViewModel BuildVm(StubWorkerClient worker)
-        => new MissionControlViewModel(new TestDbFactory(NewContext), worker);
+        => new MissionControlViewModel(new TestDbFactory(NewContext), worker, new UsagePillViewModel(worker));
 
     // ── acceptance criterion (a): TaskStarted must NOT add a pane ──────────────
 

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

@@ -0,0 +1,128 @@
+using System;
+using ClaudeDo.Ui.Services;
+using ClaudeDo.Ui.ViewModels;
+using Xunit;
+
+namespace ClaudeDo.Ui.Tests.ViewModels;
+
+public class UsagePillViewModelTests
+{
+    private sealed class FakeWorker : StubWorkerClient
+    {
+        public UsageSnapshotDto? InitialSnapshot;
+        public override Task<UsageSnapshotDto?> GetUsageSnapshotAsync() => Task.FromResult(InitialSnapshot);
+    }
+
+    private static UsageSnapshotDto Snapshot(
+        double? fiveHourPercent = null,
+        DateTimeOffset? fiveHourResetsAt = null,
+        double? sevenDayPercent = null,
+        DateTimeOffset? sevenDayResetsAt = null,
+        int fiveHourThresholdPct = 80,
+        int sevenDayThresholdPct = 90,
+        bool isGateBlocked = false,
+        string? gateReason = null,
+        DateTime? fetchedAtUtc = null,
+        bool isStale = false,
+        string? lastError = null)
+        => new(
+            fiveHourPercent, fiveHourResetsAt, sevenDayPercent, sevenDayResetsAt,
+            Array.Empty<UsageLimitDto>(), fiveHourThresholdPct, sevenDayThresholdPct,
+            isGateBlocked, gateReason, fetchedAtUtc ?? DateTime.UtcNow, isStale, lastError);
+
+    // ── Text formatting ─────────────────────────────────────────────────────
+
+    [Fact]
+    public void Text_BothBucketsKnown_ShowsBoth()
+    {
+        var worker = new FakeWorker { InitialSnapshot = Snapshot(fiveHourPercent: 30, sevenDayPercent: 57) };
+        var vm = new UsagePillViewModel(worker);
+
+        Assert.Contains("5h", vm.Text);
+        Assert.Contains("30", vm.Text);
+        Assert.Contains("7d", vm.Text);
+        Assert.Contains("57", vm.Text);
+    }
+
+    [Fact]
+    public void Text_OnlyFiveHourKnown_ShowsOnlyFiveHour()
+    {
+        var worker = new FakeWorker { InitialSnapshot = Snapshot(fiveHourPercent: 42) };
+        var vm = new UsagePillViewModel(worker);
+
+        Assert.Contains("5h", vm.Text);
+        Assert.Contains("42", vm.Text);
+        Assert.DoesNotContain("7d", vm.Text);
+    }
+
+    [Fact]
+    public void Text_NoSnapshot_ShowsEmptyPlaceholder()
+    {
+        var worker = new FakeWorker();
+        var vm = new UsagePillViewModel(worker);
+
+        Assert.Equal("Usage –", vm.Text);
+    }
+
+    // ── IsWarn / IsBlocked threshold logic ──────────────────────────────────
+
+    [Fact]
+    public void IsWarn_BelowThresholdMinusTen_IsFalse()
+    {
+        var worker = new FakeWorker { InitialSnapshot = Snapshot(fiveHourPercent: 69, fiveHourThresholdPct: 80) };
+        var vm = new UsagePillViewModel(worker);
+
+        Assert.False(vm.IsWarn);
+        Assert.False(vm.IsBlocked);
+    }
+
+    [Fact]
+    public void IsWarn_AtThresholdMinusTen_IsTrue()
+    {
+        var worker = new FakeWorker { InitialSnapshot = Snapshot(fiveHourPercent: 70, fiveHourThresholdPct: 80) };
+        var vm = new UsagePillViewModel(worker);
+
+        Assert.True(vm.IsWarn);
+        Assert.False(vm.IsBlocked);
+    }
+
+    [Fact]
+    public void IsBlocked_WhenGateReportsBlocked_IsTrue()
+    {
+        var worker = new FakeWorker
+        {
+            InitialSnapshot = Snapshot(fiveHourPercent: 80, fiveHourThresholdPct: 80, isGateBlocked: true, gateReason: "5h-Limit 80% >= 80%")
+        };
+        var vm = new UsagePillViewModel(worker);
+
+        Assert.True(vm.IsBlocked);
+    }
+
+    // ── Stale ────────────────────────────────────────────────────────────────
+
+    [Fact]
+    public void Stale_Snapshot_SetsIsStale_AndTooltipMentionsStamp()
+    {
+        var fetchedAt = new DateTime(2026, 8, 5, 9, 41, 0, DateTimeKind.Utc);
+        var worker = new FakeWorker { InitialSnapshot = Snapshot(isStale: true, fetchedAtUtc: fetchedAt, lastError: "timeout") };
+        var vm = new UsagePillViewModel(worker);
+
+        Assert.True(vm.IsStale);
+        Assert.Contains(fetchedAt.ToLocalTime().ToString("HH:mm"), vm.Tooltip);
+        Assert.Contains("timeout", vm.Tooltip);
+    }
+
+    // ── UsageUpdated event ───────────────────────────────────────────────────
+
+    [Fact]
+    public void UsageUpdated_Event_UpdatesText()
+    {
+        var worker = new FakeWorker();
+        var vm = new UsagePillViewModel(worker);
+        Assert.Equal("Usage –", vm.Text);
+
+        worker.RaiseUsageUpdated(Snapshot(fiveHourPercent: 12));
+
+        Assert.Contains("12", vm.Text);
+    }
+}