fix(active_job): save and restore hub around job execution

This correctly handles all execution modes:
- Dedicated async workers (new thread, nil hub): clone -> restore nil
- Inline inside a Rack request (rack hub on thread): clone -> restore
  rack hub so the HTTP response completes normally
- Thread-pool workers (recycled thread, stale hub): clone -> restore
  stale hub (irrelevant; next job will clone again)

Co-Authored-By: github-copilot <noreply@example.com>

Author: solnic

sentry-rails/lib/sentry/rails/active_job.rb

@@ -98,7 +98,14 @@ def record_producer_span(job)
           end
 
           def record(job, trace_headers: nil, user: nil, &block)
-            Sentry.clone_hub_to_current_thread if Thread.current != Thread.main
+            # Always give this thread a fresh hub cloned from the main hub so
+            # the job's events are fully isolated.  Save and restore whatever
+            # hub was on the thread before (e.g. the Rack request hub set by
+            # CaptureExceptions, or a stale hub left by a recycled thread-pool
+            # thread) so the outer context continues working correctly after
+            # the job finishes.
+            original_hub = Thread.current.thread_variable_get(Sentry::THREAD_LOCAL)
+            Sentry.clone_hub_to_current_thread
 
             Sentry.with_scope do |scope|
               begin
@@ -142,6 +149,8 @@ def record(job, trace_headers: nil, user: nil, &block)
                 raise
               end
             end
+          ensure
+            Thread.current.thread_variable_set(Sentry::THREAD_LOCAL, original_hub)
           end
 
           def set_messaging_data(transaction, job)