Add CMS comparison matrix page (#846)

* feat(www): add headless CMS comparison matrix page

Add /compare — an honest, exhaustive feature matrix comparing SonicJS,
Payload, Strapi, Directus, Sanity, and Contentful across 125+ capabilities
in 13 categories (architecture, pricing, content modeling, editorial, APIs,
auth, media, i18n, admin UI, extensibility, DX, security, ecosystem).

- New ComparisonMatrix component with Built-in/Partial/Plugin/Paid/Roadmap
  status badges + legend; SonicJS column highlighted
- Neutral, gap-analysis framing that surfaces where competitors lead
- SEO: page metadata + keywords, FAQPage + BreadcrumbList JSON-LD, visible
  FAQ section, canonical, OG/Twitter, sitemap entry, global metadataBase
- Cross-link /compare from 10 CMS comparison blog posts (and back)
- Add "Compare" to Resources nav

Also fixes a pre-existing CodePanel crash (Children.only 500'd MDX pages on
dev) and makes the docs dev server runnable standalone (next dev --webpack +
port-3010 cleanup in predev).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix(www): make all 6 comparison columns discoverable

The 6-column matrix overflowed the prose width, hiding Sanity & Contentful
off-screen. Break the table out to full content width on large screens (all
columns visible at >=1280px), tighten cell padding, lower min-width, and add
a 'scroll sideways' hint on narrower viewports.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* docs(www): link /compare matrix from NestJS/Hono comparison post

Completes coverage — all 11 CMS/framework comparison posts now reference
the feature matrix.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix: polish comparison matrix docs page

- Make the CMS comparison header sticky while scrolling the matrix

- Keep docs dev on webpack and make www config explicitly ESM

Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: lane711

www/package.json

@@ -3,6 +3,7 @@
   "version": "2.0.1",
   "description": "Official documentation website for SonicJS headless CMS",
   "private": true,
+  "type": "module",
   "engines": {
     "node": ">=20.0.0",
     "npm": ">=10.0.0"

www/postcss.config.js

@@ -1,4 +1,4 @@
-module.exports = {
+export default {
   plugins: {
     '@tailwindcss/postcss': {},
   },

www/prettier.config.js

@@ -1,5 +1,5 @@
 /** @type {import('prettier').Options} */
-module.exports = {
+export default {
   singleQuote: true,
   semi: false,
   plugins: ['prettier-plugin-organize-imports', 'prettier-plugin-tailwindcss'],