feat(ui): warn when the running worker predates the selected repo's merged HEAD

Stamps ClaudeDo.Worker's build with its exact git SHA (SourceRevisionId ->
InformationalVersion) and exposes it via a new GetWorkerBuildInfo hub call.
For the currently selected list, the shell compares that SHA against the
list's git HEAD (GitService.IsAncestorAsync) and shows a persistent footer
banner -- never auto-clearing, never shown on an unrelated repo or when the
ancestry can't be determined -- so "verified against a merge" claims aren't
silently made against a stale process. No auto-restart; the banner just
offers the existing RestartWorkerCommand.

tests/ClaudeDo.Ui.Tests/StaleWorkerBannerDecisionTests.cs

@@ -0,0 +1,47 @@
+using ClaudeDo.Ui.ViewModels;
+using Xunit;
+
+namespace ClaudeDo.Ui.Tests;
+
+public class StaleWorkerBannerDecisionTests
+{
+    private const string ShaA = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
+    private const string ShaB = "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb";
+
+    [Fact]
+    public void True_when_build_is_a_strict_ancestor_of_head()
+    {
+        Assert.True(IslandsShellViewModel.ShouldShowStaleWorkerBanner(ShaA, ShaB, isAncestor: true));
+    }
+
+    [Fact]
+    public void False_when_build_equals_head_even_if_ancestor_check_says_true()
+    {
+        Assert.False(IslandsShellViewModel.ShouldShowStaleWorkerBanner(ShaA, ShaA, isAncestor: true));
+    }
+
+    [Fact]
+    public void False_when_ancestor_check_says_no()
+    {
+        Assert.False(IslandsShellViewModel.ShouldShowStaleWorkerBanner(ShaA, ShaB, isAncestor: false));
+    }
+
+    [Fact]
+    public void False_when_ancestor_check_is_unknown()
+    {
+        // Unknown must never be treated as stale.
+        Assert.False(IslandsShellViewModel.ShouldShowStaleWorkerBanner(ShaA, ShaB, isAncestor: null));
+    }
+
+    [Fact]
+    public void False_when_build_sha_missing()
+    {
+        Assert.False(IslandsShellViewModel.ShouldShowStaleWorkerBanner(null, ShaB, isAncestor: true));
+    }
+
+    [Fact]
+    public void False_when_head_sha_missing()
+    {
+        Assert.False(IslandsShellViewModel.ShouldShowStaleWorkerBanner(ShaA, null, isAncestor: true));
+    }
+}

tests/ClaudeDo.Ui.Tests/StubWorkerClient.cs

@@ -150,6 +150,8 @@ public abstract class StubWorkerClient : IWorkerClient
     public virtual Task DeleteDailyNoteAsync(string id) => Task.CompletedTask;
     public string LastPrepLog = "";
     public virtual Task<string> GetLastPrepLogAsync() => Task.FromResult(LastPrepLog);
+    public WorkerBuildInfoDto? WorkerBuildInfo;
+    public virtual Task<WorkerBuildInfoDto?> GetWorkerBuildInfoAsync() => Task.FromResult(WorkerBuildInfo);
     public virtual Task RefineTaskAsync(string taskId) => Task.CompletedTask;
 
     public virtual Task<OnlineInboxStateDto?> GetOnlineInboxStateAsync() => Task.FromResult<OnlineInboxStateDto?>(null);

tests/ClaudeDo.Worker.Tests/Hub/WorkerBuildInfoHubTests.cs

@@ -0,0 +1,36 @@
+using ClaudeDo.Worker.Hub;
+using Xunit;
+
+namespace ClaudeDo.Worker.Tests.Hub;
+
+public sealed class WorkerBuildInfoHubTests
+{
+    [Theory]
+    [InlineData(null, null)]
+    [InlineData("", null)]
+    [InlineData("1.2.3", null)]
+    [InlineData("1.2.3+", null)]
+    [InlineData("1.2.3+abc1234", "abc1234")]
+    // MinVer's own pre-release metadata can already contain a '+' (e.g. "+devsha"); our
+    // SourceRevisionId is appended last, so only the segment after the LAST '+' is authoritative.
+    [InlineData("0.0.0-alpha.0.4+devsha+f5b1a2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9", "f5b1a2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9")]
+    public void ParseBuildSha_ExtractsSegmentAfterLastPlus(string? informationalVersion, string? expected)
+    {
+        Assert.Equal(expected, WorkerHub.ParseBuildSha(informationalVersion));
+    }
+
+    [Fact]
+    public void GetWorkerBuildInfo_ReturnsDto()
+    {
+        var hub = new WorkerHub(
+            null!, null!, null!, null!, null!, null!,
+            null!, null!, null!, null!, null!, null!, null!, null!, null!, null!, null!, null!, null!,
+            null!, new ClaudeDo.Worker.Online.OnlineInboxConfig(), new ClaudeDo.Worker.Online.OnlineTokenStore(),
+            new ClaudeDo.Worker.Runner.PendingQuestionRegistry(), null!);
+
+        // No assertion on the actual SHA value (depends on the build environment) — just that
+        // the call doesn't throw and always returns a DTO, never null.
+        var info = hub.GetWorkerBuildInfo();
+        Assert.NotNull(info);
+    }
+}

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

@@ -317,4 +317,45 @@ public class GitServiceMergeTests : IDisposable
         Assert.Equal(headBefore, GitRepoFixture.RunGit(repo.RepoDir, "rev-parse", "HEAD").Trim());
         Assert.True(string.IsNullOrWhiteSpace(GitRepoFixture.RunGit(repo.RepoDir, "status", "--porcelain")));
     }
+
+    [Fact]
+    public async Task IsAncestorAsync_EarlierCommit_ReturnsTrue()
+    {
+        if (!GitRepoFixture.IsGitAvailable()) return;
+        var repo = NewRepo();
+        var first = repo.BaseCommit;
+
+        File.WriteAllText(Path.Combine(repo.RepoDir, "second.txt"), "second\n");
+        GitRepoFixture.RunGit(repo.RepoDir, "add", "-A");
+        GitRepoFixture.RunGit(repo.RepoDir, "commit", "-m", "chore: second commit");
+
+        var git = new GitService();
+        var head = (await git.RevParseHeadAsync(repo.RepoDir)).Trim();
+
+        Assert.True(await git.IsAncestorAsync(repo.RepoDir, first, head));
+        Assert.False(await git.IsAncestorAsync(repo.RepoDir, head, first));
+    }
+
+    [Fact]
+    public async Task IsAncestorAsync_SameCommit_ReturnsTrue()
+    {
+        if (!GitRepoFixture.IsGitAvailable()) return;
+        var repo = NewRepo();
+        var git = new GitService();
+        var head = (await git.RevParseHeadAsync(repo.RepoDir)).Trim();
+
+        Assert.True(await git.IsAncestorAsync(repo.RepoDir, head, head));
+    }
+
+    [Fact]
+    public async Task IsAncestorAsync_UnknownCommit_ReturnsNull()
+    {
+        if (!GitRepoFixture.IsGitAvailable()) return;
+        var repo = NewRepo();
+        var git = new GitService();
+        var head = (await git.RevParseHeadAsync(repo.RepoDir)).Trim();
+        var bogus = new string('a', 40);
+
+        Assert.Null(await git.IsAncestorAsync(repo.RepoDir, bogus, head));
+    }
 }

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

@@ -141,6 +141,7 @@ sealed class FakeWorkerClient : IWorkerClient
     public Task UpdateDailyNoteAsync(string id, string text) => Task.CompletedTask;
     public Task DeleteDailyNoteAsync(string id) => Task.CompletedTask;
     public Task<string> GetLastPrepLogAsync() => Task.FromResult(string.Empty);
+    public Task<WorkerBuildInfoDto?> GetWorkerBuildInfoAsync() => Task.FromResult<WorkerBuildInfoDto?>(null);
     public Task RefineTaskAsync(string taskId) => Task.CompletedTask;
     public Task<OnlineInboxStateDto?> GetOnlineInboxStateAsync() => Task.FromResult<OnlineInboxStateDto?>(null);
     public Task SetOnlineInboxConfigAsync(OnlineInboxConfigInputDto input) => Task.CompletedTask;