feat(worker): broadcast interactive message queue + delivery

StreamingClaudeSession raises onQueueChanged (pending snapshot) and onUserMessageSent
(on delivery, incl. the seeded first prompt); InteractiveSessionService forwards these
as InteractiveQueueChanged/InteractiveMessageSent broadcasts. Lets the UI show queued
messages above the input and move a message into the transcript only when actually
delivered to Claude. Client events + fakes updated.

tests/ClaudeDo.Worker.Tests/Runner/StreamingClaudeSessionTests.cs

@@ -266,4 +266,141 @@ public sealed class StreamingClaudeSessionTests
 
         await session.DisposeAsync();
     }
+
+    // ──────────────────────────────────────────────────────────────────────────
+    // Callback tests (onQueueChanged / onUserMessageSent)
+    // ──────────────────────────────────────────────────────────────────────────
+
+    private static StreamingClaudeSession BuildWithCallbacks(
+        FakeClaudeStreamTransport transport,
+        List<IReadOnlyList<string>> queueChanges,
+        List<string> sent)
+    {
+        return new StreamingClaudeSession(
+            transport,
+            line => Task.CompletedTask,
+            NullLogger<StreamingClaudeSession>.Instance,
+            onQueueChanged: snapshot => queueChanges.Add(snapshot),
+            onUserMessageSent: text => sent.Add(text));
+    }
+
+    [Fact]
+    public async Task Start_InvokesOnUserMessageSent_WithFirstPrompt()
+    {
+        var transport = new FakeClaudeStreamTransport();
+        var sent = new List<string>();
+        var session = BuildWithCallbacks(transport, [], sent);
+
+        await session.StartAsync([], "/tmp", "hello", CancellationToken.None);
+
+        Assert.Single(sent);
+        Assert.Equal("hello", sent[0]);
+
+        await session.DisposeAsync();
+    }
+
+    [Fact]
+    public async Task SendWhileInFlight_InvokesOnQueueChanged_NotOnUserMessageSent()
+    {
+        var transport = new FakeClaudeStreamTransport();
+        var queueChanges = new List<IReadOnlyList<string>>();
+        var sent = new List<string>();
+        var session = BuildWithCallbacks(transport, queueChanges, sent);
+
+        await session.StartAsync([], "/tmp", "first", CancellationToken.None);
+        sent.Clear(); // ignore the initial prompt notification
+
+        await session.SendUserMessageAsync("queued-msg", CancellationToken.None);
+
+        Assert.Single(queueChanges);
+        Assert.Contains("queued-msg", queueChanges[0]);
+        Assert.DoesNotContain("queued-msg", sent);
+
+        await session.DisposeAsync();
+    }
+
+    [Fact]
+    public async Task PushResult_FlushesPending_InvokesQueueClearThenUserMessageSent()
+    {
+        var transport = new FakeClaudeStreamTransport();
+        var queueChanges = new List<IReadOnlyList<string>>();
+        var sent = new List<string>();
+        var session = BuildWithCallbacks(transport, queueChanges, sent);
+
+        await session.StartAsync([], "/tmp", "first", CancellationToken.None);
+        sent.Clear();
+
+        await session.SendUserMessageAsync("queued-msg", CancellationToken.None);
+        queueChanges.Clear(); // ignore the enqueue snapshot
+
+        await transport.PushLineAsync(ResultLine());
+
+        // After flush: one queueChanged with empty list, then sent contains flushed text.
+        Assert.Single(queueChanges);
+        Assert.Empty(queueChanges[0]);
+        Assert.Single(sent);
+        Assert.Equal("queued-msg", sent[0]);
+
+        await session.DisposeAsync();
+    }
+
+    [Fact]
+    public async Task SendWhileIdle_InvokesOnUserMessageSent_NoQueueChanged()
+    {
+        var transport = new FakeClaudeStreamTransport();
+        var queueChanges = new List<IReadOnlyList<string>>();
+        var sent = new List<string>();
+        var session = BuildWithCallbacks(transport, queueChanges, sent);
+
+        await session.StartAsync([], "/tmp", "first", CancellationToken.None);
+        await transport.PushLineAsync(ResultLine()); // go idle
+        sent.Clear();
+        queueChanges.Clear();
+
+        await session.SendUserMessageAsync("idle-msg", CancellationToken.None);
+
+        Assert.Empty(queueChanges);
+        Assert.Single(sent);
+        Assert.Equal("idle-msg", sent[0]);
+
+        await session.DisposeAsync();
+    }
+
+    [Fact]
+    public async Task TwoMessagesQueued_FlushFifo_QueueSnapshotsShrink()
+    {
+        var transport = new FakeClaudeStreamTransport();
+        var queueChanges = new List<IReadOnlyList<string>>();
+        var sent = new List<string>();
+        var session = BuildWithCallbacks(transport, queueChanges, sent);
+
+        await session.StartAsync([], "/tmp", "first", CancellationToken.None);
+        sent.Clear();
+
+        await session.SendUserMessageAsync("second", CancellationToken.None);
+        await session.SendUserMessageAsync("third", CancellationToken.None);
+        // queueChanges[0] = ["second"], queueChanges[1] = ["second","third"]
+        Assert.Equal(2, queueChanges.Count);
+        Assert.Equal(new[] { "second" }, queueChanges[0]);
+        Assert.Equal(new[] { "second", "third" }, queueChanges[1]);
+        queueChanges.Clear();
+
+        // Result 1 → flushes "second"; remaining queue = ["third"]
+        await transport.PushLineAsync(ResultLine());
+        Assert.Single(queueChanges);
+        Assert.Equal(new[] { "third" }, queueChanges[0]);
+        Assert.Single(sent);
+        Assert.Equal("second", sent[0]);
+        sent.Clear();
+        queueChanges.Clear();
+
+        // Result 2 → flushes "third"; remaining queue = []
+        await transport.PushLineAsync(ResultLine());
+        Assert.Single(queueChanges);
+        Assert.Empty(queueChanges[0]);
+        Assert.Single(sent);
+        Assert.Equal("third", sent[0]);
+
+        await session.DisposeAsync();
+    }
 }

tests/ClaudeDo.Worker.Tests/UiVm/TasksIslandViewModelPlanningTests.cs

@@ -38,6 +38,8 @@ sealed class FakeWorkerClient : IWorkerClient
     public event Action<string, string>? TaskQuestionResolvedEvent;
     public event Action<string>? InteractiveSessionStartedEvent;
     public event Action<string>? InteractiveSessionEndedEvent;
+    public event Action<string, IReadOnlyList<string>>? InteractiveQueueChangedEvent;
+    public event Action<string, string>? InteractiveMessageSentEvent;
     public void RaiseTaskUpdated(string taskId) => TaskUpdatedEvent?.Invoke(taskId);
     public void RaiseWorktreeUpdated(string taskId) => WorktreeUpdatedEvent?.Invoke(taskId);
     public void RaiseTaskMessage(string taskId, string line) => TaskMessageEvent?.Invoke(taskId, line);