fix(windows): tighten WebView2 idle hooks from #273 review (#276)

- Type `window.__psyHidden` once via global declaration; drop 6 `(window as any)` casts.
- `WindowVisibilityProvider` now ORs `window.__psyHidden` into the hidden state
  (and into the initial state). On WebView2 `document.hidden` does not always
  flip when `win.hide()` is called, so effects gated by `useWindowVisibility()`
  can now actually skip creating intervals/rAF instead of relying solely on the
  per-tick fallback check.
- Slow visible-poll from 200 ms to 500 ms (5 → 2 wakeups/s for visibility alone).
- Fix stray leading-space indent in `App.tsx` `window:close-requested` comment.

Co-authored-by: Psychotoxical <dev@psysonic.app>

src/components/WaveformSeek.tsx

@@ -750,7 +750,7 @@ export function SeekbarPreview({
       }
     };
     const tick = () => {
-      if (document.hidden || (window as any).__psyHidden) {
+      if (document.hidden || window.__psyHidden) {
         pollId = window.setTimeout(() => {
           pollId = null;
           tick();
@@ -900,7 +900,7 @@ export default function WaveformSeek({ trackId }: Props) {
       }
     };
     const tick = () => {
-      if (document.hidden || (window as any).__psyHidden) {
+      if (document.hidden || window.__psyHidden) {
         pollId = window.setTimeout(() => {
           pollId = null;
           tick();