feat(ui): shared ListPane primitive + misc polish

ListPane is a compound component (Header / TitleRow / Title / Actions /
Search / Scroll) that owns the relative wrapper, faded right divider
(50px top fade), top scroll mask, and absolute-positioned header used by
every list-detail tab. Wires up CapturesTab, StoryList, and EffectsList.
EffectsTab gets -mx-8 / pr-8 to match the edge-to-edge layout used
elsewhere.

Other changes:
- MCPPage: native <select> → shadcn <Select> for default voice and
  per-binding voice pickers
- Button outline variant: add hover:border-accent
- Drop hover:text-destructive from trailing delete buttons
  (HistoryTable, GpuAcceleration, GpuPage, EffectsChainEditor,
  EffectsDetail)
- HistoryTable empty state moved behind t('history.empty')
- StoryContent scroll padding pt-14 → pt-16
- backend health reports the captures dir
- landing CapturesMockup: "Send to" → "Export" with Download icon
- CHANGELOG: drop [Unreleased] personality section

landing/src/components/CapturesMockup.tsx

@@ -9,8 +9,8 @@ import {
   Copy,
   FileAudio,
   Mic,
+  Download,
   Play,
-  Send,
   Settings,
   Sparkles,
   Subtitles,
@@ -394,8 +394,8 @@ function DetailView({ capture }: { capture: Capture }) {
           Re-refine
         </div>
         <div className="inline-flex items-center gap-2 h-9 px-3 rounded-full border border-input bg-background text-sm font-medium text-foreground whitespace-nowrap">
-          <Send className="h-3.5 w-3.5" />
-          Send to
+          <Download className="h-3.5 w-3.5" />
+          Export
         </div>
       </div>
     </div>