macos: restore window frame on cascadeTopLeft since macOS 15 moves it

Fixes #2565

This appears to be a bug in macOS 15. Specifically on macOS 15 when the
new native window snapping feature is used, `cascadeTopLeft(from: zero)`
will move the window frame back to its prior unsnapped position.

The docs for `cascadeTopLeft(from:)` explicitly say:

> When NSZeroPoint, the window is not moved, except as needed to constrain
> to the visible screen

This is not the behavior we are seeing on macOS 15. The window is on the
visible screen, we're using NSZeroPoint, and yet the window is still
being moved. This does not happen on macOS 14 (but its hard to say
exactly because macOS 14 didn't have window snapping).

This commit works around the issue by saving the window frame before
calling `cascadeTopLeft(from: zero)` and then restoring it afterwards
if it has changed.

I've also filed a radar with Apple for this issue.

macos/Sources/Features/Terminal/TerminalManager.swift

@@ -227,7 +227,19 @@ class TerminalManager {
             // are closing a tabbed window, we want to set the cascade point to be
             // the next cascade point from this window.
             if focusedWindow != controller.window {
+                // The cascadeTopLeft call below should NOT move the window. Starting with
+                // macOS 15, we found that specifically when used with the new window snapping
+                // features of macOS 15, this WOULD move the frame. So we keep track of the
+                // old frame and restore it if necessary. Issue:
+                // https://github.com/ghostty-org/ghostty/issues/2565
+                let oldFrame = focusedWindow.frame
+
                 Self.lastCascadePoint = focusedWindow.cascadeTopLeft(from: NSZeroPoint)
+
+                if focusedWindow.frame != oldFrame {
+                    focusedWindow.setFrame(oldFrame, display: true)
+                }
+
                 return
             }