Add quick-win features: copy-on-select, middle-click paste, visual bell, zoom pane, clickable URLs, draggable dividers

- Copy on select: Auto-copy selected text to clipboard
- Middle-click paste: Quick paste with middle mouse button
- Visual bell: Subtle flash when commands complete
- Zoom pane: Cmd+Shift+Enter to maximize/restore split pane
- Clickable URLs: Cmd+click to open URLs in browser
- Draggable dividers: Resize split panes by dragging divider
- Updated help and keyboard shortcuts documentation

MainWindowController.swift

@@ -50,6 +50,8 @@ class MainWindowController: NSWindowController {
     var snippetPanel: SnippetPanel!
     var aiPanel: AIGeneratorPanel!
     var settingsWindow: SettingsWindowController!
+    var zoomedPane: TerminalSession?
+    var preZoomSplitView: NSSplitView?
     
     convenience init() {
         let window = NSWindow(
@@ -202,6 +204,10 @@ class MainWindowController: NSWindowController {
         closePaneItem.keyEquivalentModifierMask = [.command, .shift]
         fileMenu.addItem(closePaneItem)
         
+        let zoomPaneItem = NSMenuItem(title: "Zoom Pane", action: #selector(toggleZoomPane), keyEquivalent: "\r")
+        zoomPaneItem.keyEquivalentModifierMask = [.command, .shift]
+        fileMenu.addItem(zoomPaneItem)
+        
         fileMenu.addItem(NSMenuItem.separator())
         fileMenu.addItem(NSMenuItem(title: "Clear Screen", action: #selector(clearScreen), keyEquivalent: "k"))
         fileMenu.addItem(NSMenuItem(title: "Clear Scrollback", action: #selector(clearScrollback), keyEquivalent: "K"))
@@ -552,6 +558,7 @@ class MainWindowController: NSWindowController {
           Cmd+W - Close Tab
           Cmd+D - Split Pane Vertically (side-by-side)
           Cmd+Shift+D - Split Pane Horizontally (top-bottom)
+          Cmd+Shift+Enter - Zoom/Unzoom Pane
           Cmd+K - Clear Screen
           Cmd+Shift+K - Clear Scrollback
         
@@ -561,6 +568,7 @@ class MainWindowController: NSWindowController {
           Cmd+A - Select All
           Cmd+F - Find in Terminal
           Cmd+R - Search History
+          Middle-click - Paste
         
         Tools:
           Cmd+K - AI Command Generator
@@ -579,6 +587,8 @@ class MainWindowController: NSWindowController {
           Up/Down - Navigate Command History
           Double-click Tab - Rename Tab
           Click × button - Close split pane
+          Cmd+Click URL - Open in browser
+          Select text - Auto-copy to clipboard
         """
         alert.alertStyle = .informational
         alert.addButton(withTitle: "OK")
@@ -602,6 +612,7 @@ class MainWindowController: NSWindowController {
             splitView?.isVertical = true  // Side-by-side (vertical divider)
             splitView?.dividerStyle = .thin
             splitView?.autoresizingMask = [.width, .height]
+            splitView?.delegate = self
             
             // Move current session to split view with close button
             currentSession.scrollView.removeFromSuperview()
@@ -646,6 +657,7 @@ class MainWindowController: NSWindowController {
             splitView?.isVertical = false  // Top-bottom (horizontal divider)
             splitView?.dividerStyle = .thin
             splitView?.autoresizingMask = [.width, .height]
+            splitView?.delegate = self
             
             // Move current session to split view with close button
             currentSession.scrollView.removeFromSuperview()
@@ -759,6 +771,53 @@ class MainWindowController: NSWindowController {
         }
     }
     
+    @objc func toggleZoomPane() {
+        if zoomedPane != nil {
+            // Unzoom - restore split view
+            unzoomPane()
+        } else {
+            // Zoom current pane
+            zoomPane()
+        }
+    }
+    
+    private func zoomPane() {
+        guard panes.count > 1 else { return }
+        
+        // Save current split view state
+        preZoomSplitView = splitView
+        zoomedPane = panes[activePaneIndex]
+        
+        // Remove split view
+        splitView?.removeFromSuperview()
+        
+        // Show only the active pane
+        if let zoomed = zoomedPane {
+            zoomed.scrollView.removeFromSuperview()
+            zoomed.scrollView.frame = contentView.bounds
+            contentView.addSubview(zoomed.scrollView)
+            zoomed.textView.window?.makeFirstResponder(zoomed.textView)
+        }
+    }
+    
+    private func unzoomPane() {
+        guard let zoomed = zoomedPane, let savedSplit = preZoomSplitView else { return }
+        
+        // Remove zoomed pane
+        zoomed.scrollView.removeFromSuperview()
+        
+        // Restore split view
+        contentView.addSubview(savedSplit)
+        savedSplit.frame = contentView.bounds
+        
+        // Clear zoom state
+        zoomedPane = nil
+        preZoomSplitView = nil
+        
+        // Focus the previously zoomed pane
+        zoomed.textView.window?.makeFirstResponder(zoomed.textView)
+    }
+    
     @objc func clearHistory() {
         let alert = NSAlert()
         alert.messageText = "Clear Command History?"
@@ -813,3 +872,19 @@ class MainWindowController: NSWindowController {
         NotificationCenter.default.removeObserver(self)
     }
 }
+
+// MARK: - NSSplitView Delegate
+extension MainWindowController: NSSplitViewDelegate {
+    func splitView(_ splitView: NSSplitView, canCollapseSubview subview: NSView) -> Bool {
+        return false
+    }
+    
+    func splitView(_ splitView: NSSplitView, constrainMinCoordinate proposedMinimumPosition: CGFloat, ofSubviewAt dividerIndex: Int) -> CGFloat {
+        return 100 // Minimum pane size
+    }
+    
+    func splitView(_ splitView: NSSplitView, constrainMaxCoordinate proposedMaximumPosition: CGFloat, ofSubviewAt dividerIndex: Int) -> CGFloat {
+        let totalSize = splitView.isVertical ? splitView.bounds.width : splitView.bounds.height
+        return totalSize - 100 // Minimum pane size
+    }
+}