fix(PopupPanel): restore focus to previous app after dismissing input panel (#55)

* fix(PopupPanel): restore focus to previous app after dismissing input panel (#53)

When using the input translation mode (⌥A), the app activates itself to
receive keyboard events. After dismissing the panel, focus was not being
returned to the user's previous working app, interrupting the workflow.

Fix by recording NSWorkspace.shared.frontmostApplication before activation
and restoring focus to the previous app after panel dismissal.

Co-authored-by: CSL <caishilin@zhihu.com>
Co-authored-by: cos <i@cosine.ren>

* fix(PopupPanel): use non-deprecated activate API and guard focus restore

- Replace deprecated activate(options:) with activate()
- Only restore focus when MoePeek is still frontmost, avoiding
  pulling focus back if user has already switched away manually
- Clean up property grouping for readability

---------

Co-authored-by: Silas <caishilin@yahoo.com>
Co-authored-by: CSL <caishilin@zhihu.com>

Author: 3 people

Sources/UI/PopupPanel/PopupPanelController.swift

@@ -14,6 +14,9 @@ final class PopupPanelController {
     private let ttsCoordinator: TTSCoordinator?
     private let settingsController: SettingsWindowController?
 
+    /// The app that was frontmost before we activated ourselves for input mode.
+    private var previouslyActiveApp: NSRunningApplication?
+
     init(
         coordinator: TranslationCoordinator,
         ttsCoordinator: TTSCoordinator? = nil,
@@ -63,6 +66,8 @@ final class PopupPanelController {
         // Input mode needs the app activated so the panel can receive keyboard events.
         // Without this, makeKeyAndOrderFront alone won't route keystrokes to our panel
         // because macOS keeps delivering them to the previously active app.
+        // Remember the previously active app so we can restore focus after dismissal.
+        previouslyActiveApp = NSWorkspace.shared.frontmostApplication
         NSApp.activate(ignoringOtherApps: true)
         panel.makeKeyAndOrderFront(nil)
 
@@ -80,6 +85,12 @@ final class PopupPanelController {
         panel = nil
         coordinator.dismiss()
         onDismiss?()
+
+        // Restore focus only when MoePeek is still frontmost (user hasn't switched away manually).
+        if let previousApp = previouslyActiveApp, NSRunningApplication.current.isActive {
+            previousApp.activate()
+        }
+        previouslyActiveApp = nil
     }
 
     var isVisible: Bool {