fix: implement standard autocomplete dismiss behavior

Implemented VSCode/IntelliJ-style autocomplete behavior to fix duplicate windows and improve UX.

**Features:**
- Standard dismiss pattern: keep open when clicking sidebar/panels, dismiss only on text cursor move, invalid chars, or ESC
- Fixed duplicate windows by dismissing old window before showing new one in SQLCompletionWindowController
- Tab switch dismisses all autocomplete windows via NotificationCenter broadcast
- Added mouseDown override in EditorTextView to detect clicks at different cursor positions

**Technical changes:**
- EditorTextView: Added onClickOutsideCompletion callback and mouseDown override
- EditorCoordinator: Wired callbacks, added tab switch notification observer, simplified showCompletions logic
- MainContentView: Post QueryTabDidChange notification on tab switch
- SQLCompletionWindowController: Dismiss existing window before showing new one

Autocomplete now behaves like professional code editors with no duplicate windows.

Author: datlechin

OpenTable/Views/Editor/EditorCoordinator.swift

@@ -84,6 +84,27 @@ final class EditorCoordinator: NSObject, NSTextViewDelegate {
         textView.onKeyEvent = { [weak self] event in
             self?.handleKeyEvent(event) ?? false
         }
+        
+        textView.onClickOutsideCompletion = { [weak self] in
+            self?.dismissCompletion()
+        }
+        
+        // Observe tab switch to dismiss completion (prevents duplicate windows)
+        NotificationCenter.default.addObserver(
+            self,
+            selector: #selector(handleTabSwitch),
+            name: NSNotification.Name("QueryTabDidChange"),
+            object: nil
+        )
+    }
+    
+    deinit {
+        NotificationCenter.default.removeObserver(self)
+    }
+    
+    @objc private func handleTabSwitch() {
+        // Dismiss completion when switching tabs to prevent duplicates
+        dismissCompletion()
     }
 
     // MARK: - NSTextViewDelegate
@@ -163,7 +184,6 @@ final class EditorCoordinator: NSObject, NSTextViewDelegate {
             let prevIndex = text.index(text.startIndex, offsetBy: cursorPosition - 1)
             let prevChar = text[prevIndex]
             if prevChar == ";" || prevChar == "\n" {
-                // Check if we're at the very end or just after semicolon/newline with no new content
                 let afterCursor = String(text[text.index(text.startIndex, offsetBy: cursorPosition)...])
                     .trimmingCharacters(in: .whitespacesAndNewlines)
                 if afterCursor.isEmpty || cursorPosition == text.count {
@@ -189,7 +209,7 @@ final class EditorCoordinator: NSObject, NSTextViewDelegate {
             return
         }
 
-        // Show completion window
+        // Show completion window (window controller handles dismissing old window if needed)
         completionWindow.showCompletions(context.items, at: screenPoint, relativeTo: textView.window)
     }
 

OpenTable/Views/Editor/EditorTextView.swift

@@ -21,6 +21,9 @@ final class EditorTextView: NSTextView {
     /// Callback for handling key events (returns true if handled)
     var onKeyEvent: ((NSEvent) -> Bool)?
 
+    /// Callback when user clicks at a different position (to dismiss completion)
+    var onClickOutsideCompletion: (() -> Void)?
+    
     // MARK: - Auto-Pairing Configuration
 
     private let bracketPairs: [Character: Character] = [
@@ -186,6 +189,23 @@ final class EditorTextView: NSTextView {
         }
     }
 
+    // MARK: - Mouse Input
+    
+    override func mouseDown(with event: NSEvent) {
+        // Dismiss autocomplete when clicking at a different position in the text editor
+        // This matches VSCode/IntelliJ behavior - clicking sidebar/tabs won't dismiss
+        let clickLocation = convert(event.locationInWindow, from: nil)
+        let characterIndex = characterIndexForInsertion(at: clickLocation)
+        
+        // If click is far from current cursor position, dismiss completion
+        let currentCursor = selectedRange().location
+        if abs(characterIndex - currentCursor) > 1 {
+            onClickOutsideCompletion?()
+        }
+        
+        super.mouseDown(with: event)
+    }
+    
     // MARK: - Keyboard Input
 
     override func keyDown(with event: NSEvent) {

OpenTable/Views/Editor/SQLCompletionWindowController.swift

@@ -55,6 +55,13 @@ final class SQLCompletionWindowController: NSObject {
         self.items = items
         self.selectedIndex = 0
 
+        // CRITICAL: Dismiss existing window first to prevent duplicates
+        // This ensures only one window exists at a time
+        if window?.isVisible == true {
+            window?.parent?.removeChildWindow(window!)
+            window?.orderOut(nil)
+        }
+        
         // Create or update window
         if window == nil {
             createWindow()

OpenTable/Views/MainContentView.swift

@@ -198,6 +198,9 @@ struct MainContentView: View {
                 // Must be synchronous - save state BEFORE SwiftUI updates the view
                 handleTabChange(oldTabId: oldTabId, newTabId: newTabId)
 
+                // Dismiss all autocomplete windows to prevent duplicates
+                NotificationCenter.default.post(name: NSNotification.Name("QueryTabDidChange"), object: nil)
+                
                 // Sync selected tab ID to session for persistence
                 if let sessionId = DatabaseManager.shared.currentSessionId {
                     DatabaseManager.shared.updateSession(sessionId) { session in