Fix L6/L12: Select size=large variant, command palette scroll-into-view

L6: Select.tsx adds a `size` prop ('medium' | 'large'). When size='large',
    the select is 40px tall (matching Fluent size='large' Input/Button) with
    slightly larger padding and font. DownloadBar quality/format selects now
    use size='large' so they align with the row's large Input and buttons.

L12: CommandPalette keyboard navigation now scrolls the highlighted item into
     view on each ArrowUp/ArrowDown press. Uses a listRef + data-sel attribute
     so no DOM imperative tracking of individual buttons is needed.

typecheck + 242 tests + eslint green.

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

src/renderer/src/components/Select.tsx

@@ -1,9 +1,9 @@
-import { makeStyles, mergeClasses, tokens, shorthands } from '@fluentui/react-components'
+import { makeStyles, mergeClasses, tokens, shorthands } from '@fluentui/react-components'
 
 // A native <select> styled to match Fluent inputs. We use this instead of
 // Fluent's <Dropdown> because Fluent's portal/popover menu is a composited
 // overlay in the WebContents, and on this dev machine's GPU/driver that overlay
-// paint blanks the whole window (same family as the documented flicker —
+// paint blanks the whole window (same family as the documented flicker --
 // hardware acceleration is already disabled; see memory "aerofetch-gpu-flicker").
 // The native <select> popup is drawn by the OS, so it can't trigger the blank.
 // The popup's light/dark styling follows the `color-scheme` set on the app root
@@ -27,6 +27,11 @@ const useStyles = makeStyles({
       outline: 'none',
       ...shorthands.borderColor(tokens.colorCompoundBrandStroke)
     }
+  },
+  large: {
+    height: '40px',
+    padding: '0 12px',
+    fontSize: tokens.fontSizeBase400
   }
 })
 
@@ -41,6 +46,7 @@ interface SelectProps {
   onChange: (value: string) => void
   className?: string
   'aria-label'?: string
+  size?: 'medium' | 'large'
 }
 
 export function Select({
@@ -48,12 +54,13 @@ export function Select({
   options,
   onChange,
   className,
-  'aria-label': ariaLabel
+  'aria-label': ariaLabel,
+  size
 }: SelectProps): React.JSX.Element {
   const styles = useStyles()
   return (
     <select
-      className={mergeClasses(styles.select, className)}
+      className={mergeClasses(styles.select, size === 'large' && styles.large, className)}
       value={value}
       onChange={(e) => onChange(e.target.value)}
       aria-label={ariaLabel}