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.

src/ClaudeDo.Worker/ClaudeDo.Worker.csproj

@@ -35,18 +35,4 @@
     <InternalsVisibleTo Include="ClaudeDo.Worker.Tests" />
   </ItemGroup>
 
-  <!-- Stamps this worker's exact commit into AssemblyInformationalVersion as "+{sha}" so a
-       running instance can report which commit it was built from (see WorkerHub.GetWorkerBuildInfo).
-       Independent of MinVer: MinVerVersionOverride (release builds) replaces the base version but
-       doesn't touch SourceRevisionId, and the SDK appends it to InformationalVersion regardless. -->
-  <Target Name="SetBuildRevisionFromGit" BeforeTargets="GetAssemblyVersion" Condition="'$(SourceRevisionId)' == ''">
-    <Exec Command="git rev-parse HEAD"
-          WorkingDirectory="$(MSBuildProjectDirectory)"
-          ConsoleToMSBuild="true"
-          StandardOutputImportance="low"
-          ContinueOnError="WarnAndContinue">
-      <Output TaskParameter="ConsoleOutput" PropertyName="SourceRevisionId" />
-    </Exec>
-  </Target>
-
 </Project>