fix(picker): activate app and cleanup observer before showing

- Call NSApp.activate(ignoringOtherApps: true) to ensure picker shows
- Remove old observer before adding new one to prevent duplicates

Author: 1313

swift-bridge/Sources/ScreenCaptureKitBridge/ContentSharingPicker.swift

@@ -158,8 +158,16 @@ public func showContentSharingPicker(
     let configBox: Box<SCContentSharingPickerConfiguration> = unretained(config)
 
     DispatchQueue.main.async {
+        // Activate the app to ensure picker can show
+        NSApp.activate(ignoringOtherApps: true)
+        
         let picker = SCContentSharingPicker.shared
 
+        // Remove old observer if any
+        if let old = currentObserver {
+            picker.remove(old)
+        }
+        
         let observer = PickerObserver(callback: callback, userData: userData)
         currentObserver = observer
 
@@ -181,8 +189,16 @@ public func showContentSharingPickerWithResult(
     let configBox: Box<SCContentSharingPickerConfiguration> = unretained(config)
 
     DispatchQueue.main.async {
+        // Activate the app to ensure picker can show
+        NSApp.activate(ignoringOtherApps: true)
+        
         let picker = SCContentSharingPicker.shared
 
+        // Remove old observer if any
+        if let old = currentObserver {
+            picker.remove(old)
+        }
+        
         let observer = PickerObserverWithResult(callback: callback, userData: userData)
         currentObserver = observer