Update Rails to main

Rails main (e3d5c569) moves Campfire's pin forward ten months. Because
Campfire loads the 8.2 framework defaults, the ones added since then take
effect too, among them header-only forgery protection, Herb as the HTML
template engine, strict Accept headers and immediate blob analysis.

Changes it needed:

- Minitest 6 has no minitest/unit; the test helper no longer requires it.
- Rack::Sendfile is no longer in the middleware stack; DebugLocks goes
  before ActionDispatch::Executor, as the Rails guide now says.
- Time::DATE_FORMATS is deprecated; :epoch is registered through
  ActiveSupport::TimeFormats.
- Channel test subscriptions expose stream_names; streams is private.
- sentry-rails declares its Action Cable handle_open and handle_close
  wrappers private, which Rails 8.2 calls from outside the connection, so
  no /cable connection succeeded. An initializer makes them public until
  getsentry/sentry-ruby#2972 ships (issue #2975).
- Lexxy renders editor content through Rails' editor adapter when Rails
  has one, which asks a mention for its editor partial. It is the same
  users/mention partial the mention prompt already inserts.
- redis-client moves to 0.30.1: Rails main's Redis cache store, which
  production uses, requires 0.28.0 or later, and assets:precompile
  (the Docker build) aborted on 0.25.2.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
(cherry picked from commit b4d3880a3d88059dd5b0b884f1f5f1a6f82aa95c)

test/channels/unread_rooms_channel_test.rb

@@ -8,7 +8,7 @@ class UnreadRoomsChannelTest < ActionCable::Channel::TestCase
 
     assert subscription.confirmed?
     assert_has_stream "user_#{users(:jz).id}_unreads"
-    assert_not_includes subscription.streams, "unread_rooms"
+    assert_not_includes subscription.stream_names, "unread_rooms"
   end
 
   test "an outsider is not told about activity in a room they can't see" do
@@ -37,7 +37,7 @@ class UnreadRoomsChannelTest < ActionCable::Channel::TestCase
       stub_connection(current_user: user)
       subscribe
 
-      stream = subscription.streams.sole
+      stream = subscription.stream_names.sole
       before = ActionCable.server.pubsub.broadcasts(stream).size
 
       yield

test/test_helper.rb

@@ -2,7 +2,6 @@ ENV["RAILS_ENV"] ||= "test"
 require_relative "../config/environment"
 
 require "rails/test_help"
-require "minitest/unit"
 require "mocha/minitest"
 require "webmock/minitest"
 require "turbo/broadcastable/test_helper"