fix(overlay): restore macOS Yomitan popup focus without breaking click-a

- On macOS, skip blur-triggered focus reclaim so click-away closes popup cleanly
- Reclaim focus on popup shown event instead (card mining / reload case)
- Route focusMainWindow through focusMacOSOverlayWindow on darwin
- Refactor blur/focus test into shared harness; add macOS-specific cases

changes/macos-yomitan-popup-focus.md

@@ -0,0 +1,4 @@
+type: fixed
+area: overlay
+
+- Fixed macOS Yomitan popup focus after card mining or popup reload while still allowing click-away to close the popup without a hide/reappear cycle.