Shared RichTextEditor gains @tiptap/extension-text-align for heading and
paragraph nodes, serializing alignment as inline text-align on the block
node so it round-trips through save/reload. Fixed once at the shared
component so it also flows into the upcoming rich_text and two_column
page blocks.
Server sanitize allowlist now permits `style` on p/h1-h6, constrained by
allowedStyles to text-align (left/right/center/justify) only; all other
CSS properties and values are stripped.
Step 1 of the CMS Page Builder spec.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>