refactor(ui): remove the stale-worker banner

The banner compared the running worker's build SHA against the
selected list's HEAD via a git ancestor check on every list switch
and reconnect. It added a git-rev-parse MSBuild target, a hub call,
and a poll loop for a corner case that hasn't come up in practice —
not worth the moving parts.

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

@@ -1,36 +0,0 @@
-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.OnlineRefreshTokenStore(new ClaudeDo.Worker.DpapiTokenStore("unused.token")),
-            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);
-    }
-}