feat(whats-new): remote release notes with dev workspace mode (#1058)

* feat(whats-new): remote release notes with dev workspace mode

Add WHATS_NEW.md, CI whats-new.md asset upload, and client fetch/cache
with embedded fallbacks. Dev and -dev builds read the full file from the
repo for debugging; RC/stable download the release asset on first use.

* fix(whats-new): render ## headings and add changelog tab

Parse h2 sections in release-notes markdown; load changelog alongside
highlights and let users switch views on the What's New page.

* fix(whats-new): prefetch on startup and fix CI typecheck prebuild

Prefetch whats-new asset when the shell loads on RC/stable builds.
Run prebuild:release-notes before tsc and coverage jobs so the
gitignored generated bundle exists in CI.

* docs: CHANGELOG and credits for What's New remote notes (PR #1058)

* fix(whats-new): always slice embedded release notes to current line

Drop full CHANGELOG embed for -dev bundles; tauri:dev still reads live
markdown from the repo. Ignore all of src/generated/ in git.

* fix(whats-new): fetch release asset via Rust to bypass CORS

Route whats-new.md download through fetch_url_bytes; rename the
technical tab label; add fetch unit tests (PR #1058 review).

src/pages/WhatsNew.tsx

@@ -1,22 +1,25 @@
-import React, { useMemo } from 'react';
+import React, { useState } from 'react';
 import { Sparkles, X } from 'lucide-react';
 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/changelog/changelogReleaseMatch';
+import { useReleaseNotes } from '../hooks/useReleaseNotes';
 import { renderChangelogBody } from '../utils/changelog/changelogMarkdown';
 
+type WhatsNewView = 'highlights' | 'changelog';
+
 export default function WhatsNew() {
   const { t } = useTranslation();
   const navigate = useNavigate();
+  const { loading, whatsNewEntry, changelogEntry } = useReleaseNotes(version);
+  const [view, setView] = useState<WhatsNewView>('highlights');
 
   const close = () => {
     if (window.history.length > 1) navigate(-1);
     else navigate('/');
   };
 
-  const entry = useMemo(() => findChangelogReleaseEntry(changelogRaw, version), []);
+  const activeEntry = view === 'highlights' ? whatsNewEntry : changelogEntry;
 
   return (
     <div className="whats-new">
@@ -24,10 +27,12 @@ export default function WhatsNew() {
         <div className="whats-new__title-row">
           <Sparkles size={20} className="whats-new__icon" />
           <div>
-            <h1 className="whats-new__title">{t('whatsNew.title')}</h1>
+            <h1 className="whats-new__title">
+              {view === 'changelog' ? t('whatsNew.changelogTitle') : t('whatsNew.title')}
+            </h1>
             <div className="whats-new__subtitle">
               v{version}
-              {entry?.date && <span className="whats-new__date"> · {entry.date}</span>}
+              {activeEntry?.date && <span className="whats-new__date"> · {activeEntry.date}</span>}
             </div>
           </div>
           <button
@@ -41,11 +46,36 @@ export default function WhatsNew() {
             <X size={18} />
           </button>
         </div>
+
+        {changelogEntry && (
+          <div className="whats-new__view-tabs" role="tablist" aria-label={t('whatsNew.viewTabsLabel')}>
+            <button
+              type="button"
+              role="tab"
+              aria-selected={view === 'highlights'}
+              className={`whats-new__view-tab${view === 'highlights' ? ' whats-new__view-tab--active' : ''}`}
+              onClick={() => setView('highlights')}
+            >
+              {t('whatsNew.viewHighlights')}
+            </button>
+            <button
+              type="button"
+              role="tab"
+              aria-selected={view === 'changelog'}
+              className={`whats-new__view-tab${view === 'changelog' ? ' whats-new__view-tab--active' : ''}`}
+              onClick={() => setView('changelog')}
+            >
+              {t('whatsNew.viewChangelog')}
+            </button>
+          </div>
+        )}
       </header>
 
-      <div className="whats-new__body">
-        {entry ? (
-          renderChangelogBody(entry.body)
+      <div className="whats-new__body" role="tabpanel">
+        {loading ? (
+          <p className="whats-new__empty">{t('common.loading')}</p>
+        ) : activeEntry ? (
+          renderChangelogBody(activeEntry.body)
         ) : (
           <p className="whats-new__empty">{t('whatsNew.empty')}</p>
         )}