🤖 fix: reduce theme toggle button and title bar spacing (#702)

Restores compact layout in the top-left area while retaining the theme
toggle feature.

**Changes:**
- Reduce toggle button from 28px to 20px (`h-7` → `h-5`)
- Reduce icon from 16px to 14px (`h-4` → `h-3.5`)
- Reduce title bar vertical padding from `py-2` to `py-1`

_Generated with `mux`_

Author: ammar-agent

src/browser/components/ThemeToggleButton.tsx

@@ -12,11 +12,11 @@ export function ThemeToggleButton() {
       <button
         type="button"
         onClick={toggleTheme}
-        className="border-border-light text-muted-foreground hover:border-border-medium/80 hover:bg-toggle-bg/70 focus-visible:ring-border-medium flex h-7 w-7 items-center justify-center rounded-md border bg-transparent transition-colors duration-150 focus-visible:ring-1"
+        className="border-border-light text-muted-foreground hover:border-border-medium/80 hover:bg-toggle-bg/70 focus-visible:ring-border-medium flex h-5 w-5 items-center justify-center rounded-md border bg-transparent transition-colors duration-150 focus-visible:ring-1"
         aria-label={label}
         data-testid="theme-toggle"
       >
-        <Icon className="h-4 w-4" aria-hidden />
+        <Icon className="h-3.5 w-3.5" aria-hidden />
       </button>
       <Tooltip align="right">{label}</Tooltip>
     </TooltipWrapper>

src/browser/components/TitleBar.tsx

@@ -220,7 +220,7 @@ export function TitleBar() {
   const showUpdateIndicator = true;
 
   return (
-    <div className="bg-dark border-border-light font-primary text-muted flex shrink-0 items-center justify-between border-b px-4 py-2 text-[11px] select-none">
+    <div className="bg-dark border-border-light font-primary text-muted flex shrink-0 items-center justify-between border-b px-4 py-1 text-[11px] select-none">
       <div className="mr-4 flex min-w-0 items-center gap-2">
         {showUpdateIndicator && (
           <TooltipWrapper>