fix: resolve Quick Prompt popup visibility and model picker issues

- Replace translucent glass background with solid surface-1 color;
  backdrop-filter does not work with transparent BrowserWindows on
  Windows, leaving the panel nearly invisible
- Add data-quickprompt body attribute to quickprompt.html and CSS
  overrides to ensure body/root are truly transparent, eliminating
  the visible rectangle behind the rounded panel
- Remove overflow-hidden from qp-panel so model selector dropdown
  is no longer clipped; the dropdown was positioned absolute and
  rendered entirely outside the panel bounds
- Change ModelSelector to open downward (top-full) instead of upward
  (bottom-full) for natural command-bar flow
- Update dropdown animation direction to match downward opening
- Increase blur handler delay to 200ms for safer dropdown interactions

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/renderer/components/quick-prompt/ModelSelector.tsx

@@ -90,7 +90,7 @@ export function ModelSelector({
   return (
     <div
       ref={containerRef}
-      className="qp-dropdown-enter absolute bottom-full left-3 right-3 z-10 mb-1 overflow-hidden rounded-xl border border-[var(--color-border)] bg-[var(--color-surface-1)] shadow-2xl shadow-black/50"
+      className="qp-dropdown-enter absolute top-full left-3 right-3 z-10 mt-1 overflow-hidden rounded-xl border border-[var(--color-border)] bg-[var(--color-surface-1)] shadow-2xl shadow-black/50"
       role="listbox"
       aria-label="Select model"
     >

src/renderer/components/quick-prompt/QuickPromptApp.tsx

@@ -171,7 +171,7 @@ export function QuickPromptApp() {
   return (
     <div className="qp-container flex h-screen w-screen items-start justify-center pt-0">
       <div
-        className={`qp-panel qp-panel-enter flex w-full max-w-[680px] flex-col overflow-hidden rounded-2xl ${
+        className={`qp-panel qp-panel-enter flex w-full max-w-[680px] flex-col rounded-2xl ${
           phase === 'streaming' ? 'qp-border-streaming' : hasResponse ? 'qp-border-complete' : 'qp-border-idle'
         }`}
         role="dialog"