Track Mouse Drag Outside View (#108)

### Description

Fixes a bug that didn't allow the view to track drags outside it's bounds. Users can now drag selections over other views and outside the window.

### Related Issues

* closes #100
* closes CodeEditApp/CodeEditSourceEditor#316

### Checklist

- [x] I read and understood the [contributing guide](https://github.com/CodeEditApp/CodeEdit/blob/main/CONTRIBUTING.md) as well as the [code of conduct](https://github.com/CodeEditApp/CodeEdit/blob/main/CODE_OF_CONDUCT.md)
- [x] The issues this PR addresses are related to each other
- [x] My changes generate no new warnings
- [x] My code builds and runs on my machine
- [x] My changes are all related to the related issue above
- [x] I documented my code

### Screenshots

https://github.com/user-attachments/assets/ffbad5bf-5a56-4ef8-91f7-c5a9bb725208

Author: thecoolwinter

Sources/CodeEditTextView/TextView/TextView+Mouse.swift

@@ -87,19 +87,27 @@ extension TextView {
             return
         }
 
+        // We receive global events because our view received the drag event, but we need to clamp the potentially
+        // out-of-bounds positions to a position our layout manager can deal with.
+        let locationInWindow = convert(event.locationInWindow, from: nil)
+        let locationInView = CGPoint(
+            x: max(0.0, min(locationInWindow.x, frame.width)),
+            y: max(0.0, min(locationInWindow.y, frame.height))
+        )
+
         if mouseDragAnchor == nil {
-            mouseDragAnchor = convert(event.locationInWindow, from: nil)
+            mouseDragAnchor = locationInView
             super.mouseDragged(with: event)
         } else {
             guard let mouseDragAnchor,
                   let startPosition = layoutManager.textOffsetAtPoint(mouseDragAnchor),
-                  let endPosition = layoutManager.textOffsetAtPoint(convert(event.locationInWindow, from: nil)) else {
+                  let endPosition = layoutManager.textOffsetAtPoint(locationInView) else {
                 return
             }
 
             let modifierFlags = event.modifierFlags.intersection(.deviceIndependentFlagsMask)
             if modifierFlags.contains(.option) {
-                dragColumnSelection(mouseDragAnchor: mouseDragAnchor, event: event)
+                dragColumnSelection(mouseDragAnchor: mouseDragAnchor, locationInView: locationInView)
             } else {
                 dragSelection(startPosition: startPosition, endPosition: endPosition, mouseDragAnchor: mouseDragAnchor)
             }
@@ -197,9 +205,7 @@ extension TextView {
         }
     }
 
-    private func dragColumnSelection(mouseDragAnchor: CGPoint, event: NSEvent) {
-        // Drag the selection and select in columns
-        let eventLocation = convert(event.locationInWindow, from: nil)
-        selectColumns(betweenPointA: eventLocation, pointB: mouseDragAnchor)
+    private func dragColumnSelection(mouseDragAnchor: CGPoint, locationInView: CGPoint) {
+        selectColumns(betweenPointA: mouseDragAnchor, pointB: locationInView)
     }
 }