Add message ordering guidance to Rails docs (#288)

## Summary
- Added documentation for handling ActionCable message ordering issues
- Includes a Stimulus controller solution for client-side reordering
- Mentions async stack and AnyCable as alternatives

## Context
This PR addresses the message ordering issues discussed in #282. The
documentation includes:

1. A Stimulus controller that reorders messages based on timestamps
2. Explanation of ActionCable's ordering limitations
3. Alternative approaches (async stack, AnyCable)

## Request for Review
@ioquatix @palkan - I'd appreciate your review on the technical accuracy
of this documentation, particularly:

- Is my description of ActionCable's ordering behavior accurate?
- Are the suggested solutions appropriate?
- Any other approaches you'd recommend documenting?

## Test Plan
- [x] Documentation builds correctly
- [x] Code examples are syntactically correct
- [ ] Technical accuracy verified by domain experts

Author: crmne

docs/guides/rails.md

@@ -579,6 +579,108 @@ This setup allows for:
 2. Background processing to prevent request timeouts
 3. Automatic persistence of all messages and tool calls
 
+### Handling Message Ordering with ActionCable
+
+ActionCable does not guarantee message order due to its concurrent processing model. Messages are distributed to worker threads that deliver them to clients concurrently, which can cause out-of-order delivery (e.g., assistant responses appearing above user messages). Here are the recommended solutions:
+
+#### Option 1: Client-Side Reordering with Stimulus (Recommended)
+
+Add a Stimulus controller that maintains correct chronological order based on timestamps. This example demonstrates the concept - adapt it to your specific needs:
+
+```javascript
+// app/javascript/controllers/message_ordering_controller.js
+// Note: This is an example implementation. Test thoroughly before production use.
+import { Controller } from "@hotwired/stimulus"
+
+export default class extends Controller {
+  static targets = ["message"]
+
+  connect() {
+    this.reorderMessages()
+    this.observeNewMessages()
+  }
+
+  observeNewMessages() {
+    // Watch for new messages being added to the DOM
+    const observer = new MutationObserver((mutations) => {
+      let shouldReorder = false
+
+      mutations.forEach((mutation) => {
+        mutation.addedNodes.forEach((node) => {
+          if (node.nodeType === 1 && node.matches('[data-message-ordering-target="message"]')) {
+            shouldReorder = true
+          }
+        })
+      })
+
+      if (shouldReorder) {
+        // Small delay to ensure all attributes are set
+        setTimeout(() => this.reorderMessages(), 10)
+      }
+    })
+
+    observer.observe(this.element, { childList: true, subtree: true })
+    this.observer = observer
+  }
+
+  disconnect() {
+    if (this.observer) {
+      this.observer.disconnect()
+    }
+  }
+
+  reorderMessages() {
+    const messages = Array.from(this.messageTargets)
+
+    // Sort by timestamp (created_at)
+    messages.sort((a, b) => {
+      const timeA = new Date(a.dataset.createdAt).getTime()
+      const timeB = new Date(b.dataset.createdAt).getTime()
+      return timeA - timeB
+    })
+
+    // Reorder in DOM
+    messages.forEach((message) => {
+      this.element.appendChild(message)
+    })
+  }
+}
+```
+
+Update your views to use the controller:
+
+```erb
+<%# app/views/chats/show.html.erb %>
+<!-- Add the Stimulus controller to the messages container -->
+<div id="messages" data-controller="message-ordering">
+  <%= render @chat.messages %>
+</div>
+
+<%# app/views/messages/_message.html.erb %>
+<%= turbo_frame_tag message,
+    data: {
+      message_ordering_target: "message",
+      created_at: message.created_at.iso8601
+    } do %>
+  <!-- message content -->
+<% end %>
+```
+
+#### Option 2: Server-Side Ordering with AnyCable
+
+[AnyCable](https://anycable.io) provides order guarantees at the server level through "sticky concurrency" - ensuring messages from the same stream are processed by the same worker. This eliminates the need for client-side reordering code.
+
+#### Understanding the Root Cause
+
+As confirmed by the ActionCable maintainers, ActionCable uses a threaded executor to distribute broadcast messages, so messages are delivered to connected clients concurrently. This is by design for performance reasons.
+
+The most reliable solution is client-side reordering with order information in the payload. For applications requiring strict ordering guarantees, consider:
+- Server-sent events (SSE) for unidirectional streaming
+- WebSocket libraries with ordered stream support like [Lively](https://github.com/socketry/lively/tree/main/examples/chatbot)
+- AnyCable for server-side ordering guarantees
+
+**Note**: Some users report better behavior with the async Ruby stack (Falcon + async-cable), but this doesn't guarantee ordering and shouldn't be relied upon as a solution.
+
 ## Customizing Models
 
 Your `Chat`, `Message`, and `ToolCall` models are standard ActiveRecord models. You can add any other associations, validations, scopes, callbacks, or methods as needed for your application logic. The `acts_as` helpers provide the core persistence bridge to RubyLLM without interfering with other model behavior.