Skip AnalyzeJob when blob has no attachments

Upload-then-delete races cause AnalyzeJob to hit S3 after PurgeJob has
already removed the object, producing Aws::S3::Errors::NoSuchKey noise
in solid_queue_failed_executions. Since PurgeOnLastAttachment destroys
the attachment row before enqueueing PurgeJob, checking
blob.attachments.exists? catches this — a fast DB query that avoids the
S3 round-trip entirely.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

test/lib/rails_ext/active_storage_analyze_job_suppress_broadcasts_test.rb

@@ -0,0 +1,23 @@
+require "test_helper"
+
+class ActiveStorageAnalyzeJobSuppressBroadcastsTest < ActiveSupport::TestCase
+  test "skips analysis when blob has no attachments" do
+    blob = ActiveStorage::Blob.create_and_upload!(
+      io: StringIO.new("x" * 1024), filename: "orphan.txt", content_type: "text/plain"
+    )
+
+    blob.expects(:analyze).never
+
+    ActiveStorage::AnalyzeJob.perform_now(blob)
+  end
+
+  test "performs analysis when blob has attachments" do
+    card = cards(:logo)
+    card.image.attach io: StringIO.new("x" * 1024), filename: "test.png", content_type: "image/png"
+    blob = card.image.blob
+
+    blob.expects(:analyze).once
+
+    ActiveStorage::AnalyzeJob.perform_now(blob)
+  end
+end