Fix command modified keys. Add plan for splitscreen

Downterm/CommandNotch/Models/TerminalSession.swift

@@ -9,6 +9,7 @@ class TerminalSession: NSObject, ObservableObject, LocalProcessDelegate, @precon
     let id = UUID()
     let terminalView: TerminalView
     private var process: LocalProcess?
+    private var keyEventMonitor: Any?
     private let backgroundColor = NSColor.black
     private let configuredShellPath: String
 
@@ -26,10 +27,17 @@ class TerminalSession: NSObject, ObservableObject, LocalProcessDelegate, @precon
         let font = NSFont.monospacedSystemFont(ofSize: fontSize, weight: .regular)
         terminalView.font = font
         applyTheme(theme)
+        installCommandArrowMonitor()
 
         startShell()
     }
 
+    deinit {
+        if let keyEventMonitor {
+            NSEvent.removeMonitor(keyEventMonitor)
+        }
+    }
+
     // MARK: - Shell management
 
     private func startShell() {
@@ -58,6 +66,26 @@ class TerminalSession: NSObject, ObservableObject, LocalProcessDelegate, @precon
         return ProcessInfo.processInfo.environment["SHELL"] ?? "/bin/zsh"
     }
 
+    private func installCommandArrowMonitor() {
+        keyEventMonitor = NSEvent.addLocalMonitorForEvents(matching: .keyDown) { [weak self] event in
+            guard let self else { return event }
+            guard let window = self.terminalView.window else { return event }
+            guard event.window === window else { return event }
+            guard window.firstResponder === self.terminalView else { return event }
+
+            guard let sequence = TerminalCommandArrowBehavior.sequence(
+                for: event.modifierFlags,
+                keyCode: event.keyCode,
+                applicationCursor: self.terminalView.getTerminal().applicationCursor
+            ) else {
+                return event
+            }
+
+            self.terminalView.send(data: sequence[...])
+            return nil
+        }
+    }
+
     func updateFontSize(_ size: CGFloat) {
         terminalView.font = NSFont.monospacedSystemFont(ofSize: size, weight: .regular)
     }