Fix Windows overlay tracking, z-order, and startup visibility

- switch Windows overlay tracking to native win32 polling with native owner and z-order helpers
- keep the visible overlay and stats overlay aligned across focus handoff, transient tracker misses, and minimize/restore cycles
- start the visible overlay click-through and hide the initial opaque startup frame until the tracked transparent state settles
- add a backlog task for the inconsistent mpv y-t overlay toggle after menu toggles

src/window-trackers/base-tracker.ts

@@ -62,6 +62,10 @@ export abstract class BaseWindowTracker {
     return this.targetWindowFocused;
   }
 
+  isTargetWindowMinimized(): boolean {
+    return false;
+  }
+
   protected updateTargetWindowFocused(focused: boolean): void {
     if (this.targetWindowFocused === focused) {
       return;