Add floating close button to split panes with subtle design

- Added HoverCloseButton class with hover effects
- Close button appears in top-right corner of each split pane
- Subtle dark semi-transparent design that brightens on hover
- Container view approach for proper layout and positioning
- Updated help and keyboard shortcuts documentation
- Removed non-working Cmd+Shift+W from help displays

MainWindowController.swift

@@ -1,5 +1,44 @@
 import Cocoa
 
+// MARK: - Hover Close Button
+class HoverCloseButton: NSButton {
+    override func mouseEntered(with event: NSEvent) {
+        super.mouseEntered(with: event)
+        NSAnimationContext.runAnimationGroup { context in
+            context.duration = 0.15
+            self.layer?.backgroundColor = NSColor(white: 0.3, alpha: 0.85).cgColor
+            self.contentTintColor = NSColor.white
+        }
+    }
+    
+    override func mouseExited(with event: NSEvent) {
+        super.mouseExited(with: event)
+        NSAnimationContext.runAnimationGroup { context in
+            context.duration = 0.15
+            self.layer?.backgroundColor = NSColor(white: 0.2, alpha: 0.6).cgColor
+            self.contentTintColor = NSColor(white: 0.8, alpha: 0.9)
+        }
+    }
+    
+    override func updateTrackingAreas() {
+        super.updateTrackingAreas()
+        
+        // Remove old tracking areas
+        for trackingArea in trackingAreas {
+            removeTrackingArea(trackingArea)
+        }
+        
+        // Add new tracking area
+        let trackingArea = NSTrackingArea(
+            rect: bounds,
+            options: [.mouseEnteredAndExited, .activeAlways, .inVisibleRect],
+            owner: self,
+            userInfo: nil
+        )
+        addTrackingArea(trackingArea)
+    }
+}
+
 class MainWindowController: NSWindowController {
     var tabManager = TabManager()
     var tabBar: NSStackView!
@@ -511,9 +550,8 @@ class MainWindowController: NSWindowController {
         File:
           Cmd+T - New Tab
           Cmd+W - Close Tab
-          Cmd+D - Split Pane Vertically
+          Cmd+D - Split Pane Vertically (side-by-side)
-          Cmd+Shift+D - Split Pane Horizontally
+          Cmd+Shift+D - Split Pane Horizontally (top-bottom)
-          Cmd+Shift+W - Close Pane
           Cmd+K - Clear Screen
           Cmd+Shift+K - Clear Scrollback
         
@@ -538,7 +576,9 @@ class MainWindowController: NSWindowController {
         
         Terminal:
           Tab - Accept Auto-suggestion
+          Up/Down - Navigate Command History
           Double-click Tab - Rename Tab
+          Click × button - Close split pane
         """
         alert.alertStyle = .informational
         alert.addButton(withTitle: "OK")
@@ -563,10 +603,10 @@ class MainWindowController: NSWindowController {
             splitView?.dividerStyle = .thin
             splitView?.autoresizingMask = [.width, .height]
             
-            // Move current session to split view
+            // Move current session to split view with close button
             currentSession.scrollView.removeFromSuperview()
-            addCloseButtonToPane(currentSession.scrollView, index: 0)
+            let containerView = addCloseButtonToPane(currentSession.scrollView, index: 0)
-            splitView?.addArrangedSubview(currentSession.scrollView)
+            splitView?.addArrangedSubview(containerView)
             panes = [currentSession]
         }
         
@@ -575,8 +615,8 @@ class MainWindowController: NSWindowController {
         newSession.setupTextView(frame: CGRect(x: 0, y: 0, width: contentView.bounds.width / 2, height: contentView.bounds.height))
         newSession.startShell()
         
-        addCloseButtonToPane(newSession.scrollView, index: panes.count)
+        let newContainerView = addCloseButtonToPane(newSession.scrollView, index: panes.count)
-        splitView?.addArrangedSubview(newSession.scrollView)
+        splitView?.addArrangedSubview(newContainerView)
         panes.append(newSession)
         activePaneIndex = panes.count - 1
         
@@ -607,10 +647,10 @@ class MainWindowController: NSWindowController {
             splitView?.dividerStyle = .thin
             splitView?.autoresizingMask = [.width, .height]
             
-            // Move current session to split view
+            // Move current session to split view with close button
             currentSession.scrollView.removeFromSuperview()
-            addCloseButtonToPane(currentSession.scrollView, index: 0)
+            let containerView = addCloseButtonToPane(currentSession.scrollView, index: 0)
-            splitView?.addArrangedSubview(currentSession.scrollView)
+            splitView?.addArrangedSubview(containerView)
             panes = [currentSession]
         }
         
@@ -619,8 +659,8 @@ class MainWindowController: NSWindowController {
         newSession.setupTextView(frame: CGRect(x: 0, y: 0, width: contentView.bounds.width, height: contentView.bounds.height / 2))
         newSession.startShell()
         
-        addCloseButtonToPane(newSession.scrollView, index: panes.count)
+        let newContainerView = addCloseButtonToPane(newSession.scrollView, index: panes.count)
-        splitView?.addArrangedSubview(newSession.scrollView)
+        splitView?.addArrangedSubview(newContainerView)
         panes.append(newSession)
         activePaneIndex = panes.count - 1
         
@@ -633,29 +673,39 @@ class MainWindowController: NSWindowController {
         newSession.textView.window?.makeFirstResponder(newSession.textView)
     }
     
-    private func addCloseButtonToPane(_ scrollView: NSScrollView, index: Int) {
+    private func addCloseButtonToPane(_ scrollView: NSScrollView, index: Int) -> NSView {
-        // Remove any existing close button
+        // Create a container view that will hold both the scroll view and the close button
-        scrollView.subviews.filter { $0.tag == 9999 }.forEach { $0.removeFromSuperview() }
+        let containerView = NSView(frame: scrollView.frame)
+        containerView.autoresizingMask = [.width, .height]
+        containerView.wantsLayer = true
         
-        // Create close button
+        // Adjust scroll view frame to fill container
-        let closeButton = NSButton(frame: NSRect(x: scrollView.bounds.width - 30, y: scrollView.bounds.height - 30, width: 24, height: 24))
+        scrollView.frame = containerView.bounds
+        scrollView.autoresizingMask = [.width, .height]
+        containerView.addSubview(scrollView)
+        
+        // Create close button with subtle styling
+        let closeButton = HoverCloseButton(frame: NSRect(x: containerView.bounds.width - 35, y: containerView.bounds.height - 35, width: 24, height: 24))
         closeButton.title = "×"
         closeButton.bezelStyle = .circular
-        closeButton.font = NSFont.systemFont(ofSize: 16, weight: .bold)
+        closeButton.font = NSFont.systemFont(ofSize: 16, weight: .medium)
-        closeButton.tag = 9999  // Special tag to identify close buttons
+        closeButton.tag = 9999
         closeButton.target = self
         closeButton.action = #selector(closePaneFromButton(_:))
         closeButton.toolTip = "Close pane (Cmd+Shift+W)"
         closeButton.autoresizingMask = [.minXMargin, .minYMargin]
         closeButton.wantsLayer = true
-        closeButton.layer?.backgroundColor = NSColor.black.withAlphaComponent(0.5).cgColor
+        closeButton.layer?.backgroundColor = NSColor(white: 0.2, alpha: 0.6).cgColor
         closeButton.layer?.cornerRadius = 12
-        closeButton.contentTintColor = .white
+        closeButton.contentTintColor = NSColor(white: 0.8, alpha: 0.9)
         
         // Store the pane index
         objc_setAssociatedObject(closeButton, "paneIndex", index, .OBJC_ASSOCIATION_RETAIN)
         
-        scrollView.addSubview(closeButton)
+        // Add button on top of scroll view
+        containerView.addSubview(closeButton)
+        
+        return containerView
     }
     
     @objc func closePaneFromButton(_ sender: NSButton) {

TerminalSession.swift

@@ -568,6 +568,8 @@ class TerminalSession: NSObject, NSTextViewDelegate, NSMenuDelegate {
         Keyboard Shortcuts:
           • Cmd+T          - New tab
           • Cmd+W          - Close tab
+          • Cmd+D          - Split pane vertically (side-by-side)
+          • Cmd+Shift+D    - Split pane horizontally (top-bottom)
           • Cmd+R          - Search command history (fuzzy search)
           • Cmd+K          - AI command generator
           • Cmd+P          - Command snippets