fix(changelog): resolve embedded notes by semver core (#373)

Whats New and the post-update modal required an exact ## [version] header,
so prerelease package versions (rc, dev) often had no matching section.
Match on major.minor.patch first; if several sections share the core,
prefer a plain X.Y.Z heading when present.

src/pages/WhatsNew.tsx

@@ -4,6 +4,7 @@ import { useNavigate } from 'react-router-dom';
 import { useTranslation } from 'react-i18next';
 import { version } from '../../package.json';
 import changelogRaw from '../../CHANGELOG.md?raw';
+import { findChangelogReleaseEntry } from '../utils/changelogReleaseMatch';
 import { renderChangelogBody } from '../utils/changelogMarkdown';
 
 export default function WhatsNew() {
@@ -15,15 +16,7 @@ export default function WhatsNew() {
     else navigate('/');
   };
 
-  const entry = useMemo(() => {
-    const blocks = changelogRaw.split(/\n(?=## \[)/).filter((b: string) => b.startsWith('## ['));
-    const block = blocks.find((b: string) => b.startsWith(`## [${version}]`));
-    if (!block) return null;
-    const lines = block.split('\n');
-    const match = lines[0].match(/## \[([^\]]+)\](?:\s*-\s*(.+))?/);
-    const body = lines.slice(1).join('\n').trim();
-    return { version: match?.[1] ?? version, date: match?.[2] ?? '', body };
-  }, []);
+  const entry = useMemo(() => findChangelogReleaseEntry(changelogRaw, version), []);
 
   return (
     <div className="whats-new">
@@ -33,7 +26,7 @@ export default function WhatsNew() {
           <div>
             <h1 className="whats-new__title">{t('whatsNew.title')}</h1>
             <div className="whats-new__subtitle">
-              v{entry?.version ?? version}
+              v{version}
               {entry?.date && <span className="whats-new__date"> · {entry.date}</span>}
             </div>
           </div>