Allow clicking to position cursor within current command

- Can now click anywhere in the current command line to edit
- Useful for editing commands from history
- Clicking before prompt automatically moves cursor to prompt position
- Prevents editing previous output

TerminalSession.swift

@@ -355,6 +355,15 @@ class TerminalSession: NSObject, NSTextViewDelegate, NSMenuDelegate {
         return result
     }
     
+    func textViewDidChangeSelection(_ notification: Notification) {
+        // Allow cursor to be positioned anywhere in the current command
+        // But if user clicks before the prompt, move cursor to prompt position
+        let selectedRange = textView.selectedRange()
+        if selectedRange.location < promptPosition && selectedRange.length == 0 {
+            textView.setSelectedRange(NSRange(location: promptPosition, length: 0))
+        }
+    }
+    
     private func getCurrentCommand() -> String {
         guard promptPosition <= textView.string.count else { return "" }
         let startIndex = textView.string.index(textView.string.startIndex, offsetBy: promptPosition)