fix(macOS): filter phantom mouse events that defeat mouse-hide-while-typing (#11066)

## Summary

Ports the phantom mouse-motion position-equality check from the GTK
runtime to the embedded runtime (used by macOS).

On macOS, TUI apps like Zellij that frequently update the window title
cause phantom `mouseMoved` events at the same coordinates. These flow
through `embedded.zig` → `Surface.zig` `cursorPosCallback` →
`showMouse()`, which explicitly calls
`NSCursor.setHiddenUntilMouseMoves(false)` and unhides the cursor,
defeating `mouse-hide-while-typing`.

The GTK runtime already filters these in PR #4973 (for #3345):

```zig
const is_cursor_still = @abs(priv.cursor_pos.x - pos.x) < 1 and
    @abs(priv.cursor_pos.y - pos.y) < 1;
if (is_cursor_still) return;
```

This PR adds the same check to `embedded.zig`'s `cursorPosCallback`,
using the already-stored `self.cursor_pos` field.

## Test plan

- [x] Enable `mouse-hide-while-typing = true` in Ghostty config
- [ ] Run a TUI app that updates the window title frequently (e.g.
Zellij)
- [ ] Type — cursor should hide and stay hidden despite title updates
- [ ] Move the mouse — cursor should reappear normally
- [ ] Verify no regressions with normal mouse movement,
focus-follows-mouse, or link hovering

src/apprt/embedded.zig

@@ -848,7 +848,7 @@ pub const Surface = struct {
         mods: input.Mods,
     ) void {
         // Convert our unscaled x/y to scaled.
-        self.cursor_pos = self.cursorPosToPixels(.{
+        const pos = self.cursorPosToPixels(.{
             .x = @floatCast(x),
             .y = @floatCast(y),
         }) catch |err| {
@@ -859,6 +859,19 @@ pub const Surface = struct {
             return;
         };
 
+        // There are cases where the platform reports a mouse motion event
+        // without the cursor actually moving. For example, on macOS, updating
+        // the window title can trigger a phantom mouse-move event at the same
+        // coordinates. This can cause the mouse to incorrectly unhide when
+        // mouse-hide-while-typing is enabled (commonly seen with TUI apps
+        // like Zellij that frequently update the title). To prevent incorrect
+        // behavior, we only continue with callback logic if the cursor has
+        // actually moved.
+        if (@abs(self.cursor_pos.x - pos.x) < 1 and
+            @abs(self.cursor_pos.y - pos.y) < 1) return;
+
+        self.cursor_pos = pos;
+
         self.core_surface.cursorPosCallback(self.cursor_pos, mods) catch |err| {
             log.err("error in cursor pos callback err={}", .{err});
             return;