fix: atlas glow and AI Workspace scope pre-selection in light theme

Two targeted fixes:

- Tag Cloud atlas SVG radial gradient now switches its inner stop from white
  to a warm dark tone (rgba 60 50 30) when the Subtle Light theme is active,
  matching the explore-tag hover glow style used elsewhere in light mode.
- Switching the AI Workspace tagging queue scope to "Selected Folders" no
  longer auto-selects the first folder in the list; the selection now starts
  empty so the user can choose exactly which folders to target.

src/components/TagCloud.tsx

@@ -477,8 +477,8 @@ function TagAtlas({
       <svg className="pointer-events-none absolute inset-0 h-full w-full" aria-hidden="true">
         <defs>
           <radialGradient id="tag-atlas-glow" cx="50%" cy="50%" r="50%">
-            <stop offset="0%" stopColor="rgba(255,255,255,0.2)" />
-            <stop offset="100%" stopColor="rgba(255,255,255,0)" />
+            <stop offset="0%" stopColor={isLight ? "rgba(60,50,30,0.18)" : "rgba(255,255,255,0.2)"} />
+            <stop offset="100%" stopColor="rgba(0,0,0,0)" />
           </radialGradient>
         </defs>
         {activeNode && activeAnchor ? (