Fix L14/L20/SR10/L150: CSS baseline, client datalist, copy polish

L14: base.css gets * { box-sizing: border-box } (removes ad-hoc swatch rule),
     :focus-visible outline using the Fluent brand token color, and
     -webkit-font-smoothing / -moz-osx-font-smoothing antialiasing.

L20: youtubePlayerClient Input now has a datalist of known client names
     (web, web_safari, web_embedded, mweb, tv, ios, android) so users
     get autocomplete suggestions. Still accepts free text for future clients.

SR10: Sidebar tagline changed from 'yt-dlp frontend' to 'Video downloader'
      (plain-English, not developer shorthand).

L150: Standardized 'PO Token' capitalization -- SettingsView label now says
      'YouTube PO Token (advanced)' consistently.

typecheck + 242 tests + eslint green.

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

src/renderer/src/assets/base.css

@@ -1,9 +1,22 @@
+*,
+*::before,
+*::after {
+  box-sizing: border-box;
+}
+
+:focus-visible {
+  outline: 2px solid var(--colorBrandStroke1, #0078d4);
+  outline-offset: 2px;
+}
+
 html,
 body {
   margin: 0;
   padding: 0;
   height: 100%;
   overflow: hidden;
+  -webkit-font-smoothing: antialiased;
+  -moz-osx-font-smoothing: grayscale;
 }
 
 #root {

src/renderer/src/components/SettingsView.tsx

@@ -710,15 +710,21 @@ export function SettingsView(): React.JSX.Element {
           label="YouTube client (advanced)"
           hint="Override how AeroFetch identifies itself to YouTube when downloads start failing. Try web_safari, tv, or mweb. Leave blank for the automatic default."
         >
+          <datalist id="yt-client-list">
+            {['web', 'web_safari', 'web_embedded', 'mweb', 'tv', 'ios', 'android'].map((c) => (
+              <option key={c} value={c} />
+            ))}
+          </datalist>
           <Input
             value={youtubePlayerClient}
             placeholder="web_safari"
+            list="yt-client-list"
             onChange={(_, d) => update({ youtubePlayerClient: d.value })}
           />
         </Field>
 
         <Field
-          label="YouTube PO token (advanced)"
+          label="YouTube PO Token (advanced)"
           hint={
             potHint ??
             'A token that helps get past YouTube\'s bot check. Click "Fetch" to grab one automatically, or paste it manually. Signing in with cookies (above) is usually the easier fix.'

src/renderer/src/components/Sidebar.tsx

@@ -1,4 +1,4 @@
-import { Caption1, makeStyles, mergeClasses, tokens, shorthands } from '@fluentui/react-components'
+import { Caption1, makeStyles, mergeClasses, tokens, shorthands } from '@fluentui/react-components'
 import {
   ArrowDownloadFilled,
   ArrowDownloadRegular,
@@ -210,7 +210,7 @@ export function Sidebar({
                 string once it loads (L66); the version shows on hover and in
                 Settings → About. */}
             <Caption1 className={styles.caption} title={version ? `Version ${version}` : undefined}>
-              yt-dlp frontend
+              Video downloader
             </Caption1>
           </div>
         )}