Rework Pro page around build-free adoption, not a feature paywall (#111)

* Rework Pro page around build-free adoption, not a feature paywall

The /pro/ page framed React on Rails Pro as a locked-feature tier you
unlock by paying. That misrepresents the product: the gem and npm package
are public (bundle add react_on_rails_pro), nothing is access-gated, and an
unlicensed app keeps running and just logs its license status. A license
covers production use and maintainer support, not access.

Changes to prototypes/docusaurus/src/pages/pro.tsx (+ pro.module.css):

- Replace the misleading "Feature Comparison" OSS-vs-Pro table with an
  honest "What Pro adds" feature list: React Server Components, Streaming
  SSR, Fragment caching, dedicated Node renderer, and code splitting +
  bundle caching (the canonical "What Pro Adds" list from the upstream
  docs).
- Drop the two rows that implied documentation and the public RSC demo
  were paywalled ("React Server Components performance guides" and the
  "view-only" demo row). Guides and demos are public to everyone.
- Add a "See everything before you commit" section linking the public
  proof: the live RSC performance demo, the marketplace demo repo + its
  performance guide, and the Pro example app.
- Lead the hero with `bundle add react_on_rails_pro` and a "Free to build
  with" note; make "Start building with Pro" the single primary CTA and
  trim the hero from four competing buttons to three.
- Fix the false "Performance tier, not separate product" kicker. Pro is a
  separate, additive gem that depends on the OSS gem.
- Reword the three-step upgrade path to be build-first: add the gem, turn
  on the features you need, then license for production.

Verified with a local production build (npm run build) and a rendered
screenshot of /pro/; no new broken links or console errors.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Address PR review: fix Start-building CTA target and feature grid

Two follow-ups from automated review on PR #111:

- "Start building with Pro" now links to /docs/pro/installation instead of
  the upgrade-from-OSS guide, matching the install-and-build-fresh framing.
  Adds docsRoutes.proInstall.
- The "What Pro adds" grid had 5 cards in a 3-column layout, leaving an
  empty third slot on the second row. Switched .cardGrid to centered
  flex-wrap so the orphan row centers cleanly; the 3-card proof grid is
  unaffected.

Verified with npm run build (success, no new broken links); the built
/pro/ HTML confirms the CTA href is /docs/pro/installation.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Surface streaming-performance features on Pro page

The Pro feature grid listed generic "Streaming SSR" and "Fragment
caching" but omitted the streaming-performance work that actually
shipped in React on Rails Pro: parallel rendering via
async_react_component, immediate hydration, and caching that covers
streamed components. Name these real capabilities so the page reflects
what Pro does, and sharpen the RSC, streaming, and Node-renderer
descriptions to match.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Tighten Pro page, fix demo inconsistencies, enable Mermaid diagrams

Rework the Pro marketing page for consistency and concision, and turn on
Mermaid rendering across the docs.

Pro page (pro.tsx / pro.module.css):
- Replace the three-tile proof section with two real demos, each linking to
  both a live app and its source: LocalHub (RSC performance) and the new
  TanStack starter. The old layout split LocalHub's live demo and its repo
  into two separate tiles and showcased the spec/dummy CI fixture as an
  example app.
- Drop the spec/dummy CI test app from the marketing page.
- Cut repeated licensing / build-free copy that appeared up to five times.
  The hero highlight now covers the free side and the license card the paid
  side, with no overlap.
- Merge Immediate hydration into Streaming SSR so the feature grid is a
  balanced 3x2 (6 cards) instead of 7 with an orphan.
- Reduce three competing hero CTAs to two; the live demo now lives in the
  demo section.

examples.tsx:
- Add the TanStack starter (live demo + source repo), the strongest current
  example, which was missing from the page.

Enable Mermaid (docusaurus.config.ts / package.json / lockfile):
- Add @docusaurus/theme-mermaid and markdown.mermaid. This renders the
  existing RSC rendering-flow sequence diagram, which previously shipped as a
  raw code block, and unblocks diagrams synced from the upstream docs.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Add PR #111 before/after screenshots and RSC diagram evidence

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Make Pro feature cards discoverable

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: justin808

.github/pr-assets/pr111-pro-after-mobile.png

@@ -58,6 +58,7 @@ const config: Config = {
 
   onBrokenLinks: 'warn',
   markdown: {
+    mermaid: true,
     hooks: {
       onBrokenMarkdownLinks: 'warn',
     },
@@ -68,7 +69,7 @@ const config: Config = {
     locales: ['en'],
   },
 
-  themes: useAlgolia ? [] : [localSearchTheme],
+  themes: [...(useAlgolia ? [] : [localSearchTheme]), '@docusaurus/theme-mermaid'],
 
   presets: [
     [