Add rich-text alignment controls (left/center/right)

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>

client/package-lock.json

@@ -10,6 +10,7 @@
       "dependencies": {
         "@tiptap/extension-image": "^2.27.2",
         "@tiptap/extension-link": "^2.27.2",
+        "@tiptap/extension-text-align": "^2.27.2",
         "@tiptap/react": "^2.27.2",
         "@tiptap/starter-kit": "^2.27.2",
         "diff": "^5.2.2",
@@ -1483,6 +1484,19 @@
         "@tiptap/core": "^2.7.0"
       }
     },
+    "node_modules/@tiptap/extension-text-align": {
+      "version": "2.27.2",
+      "resolved": "https://registry.npmjs.org/@tiptap/extension-text-align/-/extension-text-align-2.27.2.tgz",
+      "integrity": "sha512-0Pyks6Hu+Q/+9+5/osoSv0SP6jIerdWMYbi13aaZLsJoj3lBj5WNaE11JtAwSFN5sx0IbqhDSlp1zkvRnzgZ8g==",
+      "license": "MIT",
+      "funding": {
+        "type": "github",
+        "url": "https://github.com/sponsors/ueberdosis"
+      },
+      "peerDependencies": {
+        "@tiptap/core": "^2.7.0"
+      }
+    },
     "node_modules/@tiptap/extension-text-style": {
       "version": "2.27.2",
       "resolved": "https://registry.npmjs.org/@tiptap/extension-text-style/-/extension-text-style-2.27.2.tgz",

client/package.json

@@ -11,6 +11,7 @@
   "dependencies": {
     "@tiptap/extension-image": "^2.27.2",
     "@tiptap/extension-link": "^2.27.2",
+    "@tiptap/extension-text-align": "^2.27.2",
     "@tiptap/react": "^2.27.2",
     "@tiptap/starter-kit": "^2.27.2",
     "diff": "^5.2.2",

client/src/components/RichTextEditor.jsx

@@ -3,6 +3,7 @@ import { useEditor, EditorContent } from '@tiptap/react'
 import StarterKit from '@tiptap/starter-kit'
 import Link from '@tiptap/extension-link'
 import Image from '@tiptap/extension-image'
+import TextAlign from '@tiptap/extension-text-align'
 import { api } from '../api/client.js'
 
 // Toolbar button.
@@ -25,6 +26,22 @@ function escapeHtml(s) {
   return String(s).replace(/[&<>"]/g, (c) => ({ '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;' })[c])
 }
 
+// Alignment glyph: three lines justified to the given side.
+function AlignIcon({ align }) {
+  const rows = {
+    left: [[2, 14], [2, 10], [2, 12]],
+    center: [[2, 14], [4, 12], [3, 13]],
+    right: [[2, 14], [6, 14], [4, 14]],
+  }[align]
+  return (
+    <svg width="15" height="15" viewBox="0 0 16 16" fill="none" stroke="currentColor" strokeWidth="1.5" strokeLinecap="round" aria-hidden="true">
+      {rows.map(([x1, x2], i) => (
+        <line key={i} x1={x1} y1={4 + i * 4} x2={x2} y2={4 + i * 4} />
+      ))}
+    </svg>
+  )
+}
+
 // Toolbar variants:
 //   'full'    — every control, incl. the internal wiki-page link picker (wiki use).
 //   'post'    — full minus the wiki-page picker (no page-list context in posts).
@@ -42,6 +59,11 @@ export default function RichTextEditor({ value, onChange, pages = [], variant =
       StarterKit.configure({ heading: { levels: [2, 3] } }),
       Link.configure({ openOnClick: false, autolink: true }),
       Image.configure({ inline: false }),
+      // Alignment stored as `text-align` on the block node (heading/paragraph),
+      // so it round-trips through save/reload as inline style. Shared here means
+      // every consumer — post editor, and the future rich_text / two_column
+      // blocks — gets it for free.
+      TextAlign.configure({ types: ['heading', 'paragraph'] }),
     ],
     content: value || '',
     onUpdate: ({ editor }) => onChange(editor.getHTML()),
@@ -131,6 +153,16 @@ export default function RichTextEditor({ value, onChange, pages = [], variant =
               —
             </Btn>
             <span className="rte-sep" />
+            <Btn title="Align left" active={editor.isActive({ textAlign: 'left' })} onClick={() => editor.chain().focus().setTextAlign('left').run()}>
+              <AlignIcon align="left" />
+            </Btn>
+            <Btn title="Align center" active={editor.isActive({ textAlign: 'center' })} onClick={() => editor.chain().focus().setTextAlign('center').run()}>
+              <AlignIcon align="center" />
+            </Btn>
+            <Btn title="Align right" active={editor.isActive({ textAlign: 'right' })} onClick={() => editor.chain().focus().setTextAlign('right').run()}>
+              <AlignIcon align="right" />
+            </Btn>
+            <span className="rte-sep" />
             <Btn title="Link" active={editor.isActive('link')} onClick={setLink}>
               🔗
             </Btn>