Simplify the docs sidebar and Pro landing pages (#3119)

### Summary

Simplify the docs information architecture by removing redundant
top-level sidebar sections, regrouping Building Features, keeping
Deployment visible, and nesting React Server Components under React on
Rails Pro. Add release note archive pages and turn `home-pro` into a
compatibility page so the sidebar can be simplified without changing
existing doc routes.

### Pull Request checklist

- [x] ~Add/update test to cover these changes~
- [x] Update documentation
- [x] ~Update CHANGELOG file~

### Other Information

Validated with `pnpm exec eslint docs/sidebars.ts`, `pnpm exec prettier
--check` on the changed files, and a doc-id existence check covering 105
sidebar references. I did not run a full Docusaurus build in this
workspace.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk documentation-only change; primary risk is broken navigation
if the stub/exclusion IDs don’t match Docusaurus doc IDs.
> 
> **Overview**
> Adds an **unlisted URL-compatibility stub** at `docs/pro/home-pro.md`
that keeps the legacy `pro/home-pro` route working and directs readers
to the canonical `pro/react-on-rails-pro` page (with a small set of Pro
quick links).
> 
> Updates sidebar exclusion configuration (`docs/.sidebar-exclusions`
and comments in `docs/sidebars.ts`) to explicitly exclude `pro/home-pro`
from navigation so it functions purely as a compatibility entry point.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
d7ed940. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Documentation**
* Added an unlisted Pro home compatibility stub that links to the
canonical Pro landing and includes a “Quick Links” section to Pro
resources (installation, OSS→Pro upgrade, React Server Components,
Streaming SSR, Node Renderer).
* Excluded the stub from the site sidebar so it serves as a
URL-compatibility redirect to the main Pro landing.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: justin808

docs/.sidebar-exclusions

@@ -23,3 +23,6 @@ misc/tips
 # Decision Guide deep-dive companions (published as supporting material, linked from comparing-react-on-rails-to-alternatives.md — see #3065)
 getting-started/comparison-with-alternatives
 getting-started/nextjs-with-separate-rails-backend
+
+# URL-compatibility stub that redirects to pro/react-on-rails-pro
+pro/home-pro

docs/pro/home-pro.md

@@ -0,0 +1,19 @@
+---
+unlisted: true
+description: Compatibility stub — use the React on Rails Pro landing page instead.
+---
+
+# React on Rails Pro Home
+
+This route is kept for compatibility with older docs links.
+
+Use [React on Rails Pro](./react-on-rails-pro.md) as the canonical Pro landing page.
+
+## Quick Links
+
+- [React on Rails Pro](./react-on-rails-pro.md)
+- [Installation](./installation.md)
+- [Upgrade from OSS to Pro](./upgrading-to-pro.md)
+- [React Server Components](./react-server-components/index.md)
+- [Streaming SSR](./streaming-ssr.md)
+- [Node Renderer](./node-renderer.md)

docs/sidebars.ts

@@ -6,6 +6,9 @@ import type { SidebarsConfig } from '@docusaurus/plugin-content-docs';
 // - deployment/troubleshooting-when-using-webpacker
 // - misc/asset-pipeline
 //
+// URL-compatibility stubs (redirect to a current, live page):
+// - pro/home-pro (→ pro/react-on-rails-pro)
+//
 // Contributing/Resources pages (linked from introduction.md instead of sidebar):
 // - misc/doctrine
 // - misc/style