Compare a preview's host to ours with the escapes resolved

Ruby leaves a percent-escape in URI#host, so "https://%77ww.example.com"
read as a different host than the one Campfire answers on while a browser
unescaped it straight back to us. A host that carries an escape, or a
trailing dot, is now measured the way the browser will read it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0186eyzivcTn6wqjEE4Wnxdt

lib/rails_ext/actiontext_opengraph_embeds.rb

@@ -38,9 +38,17 @@ class ActionText::Attachment::OpengraphEmbed
 
       # "https:/rooms/1" parses as HTTPS with no host at all, and a browser
       # resolves both that and our own hostname against the origin Campfire is
-      # served from.
+      # served from. A percent-escape hides our hostname from this comparison
+      # while a browser still unescapes it back to us, so an escaped host is out
+      # too, and neither case is anything an unfurl could have produced.
       def elsewhere?(host)
-        host.present? && !host.casecmp?(Current.request_host.to_s)
+        return false if host.blank? || host.include?("%")
+
+        canonical_host(host) != canonical_host(Current.request_host.to_s)
+      end
+
+      def canonical_host(host)
+        host.downcase.delete_suffix(".")
       end
   end