The surface's `clipboard-write` signal carries the clipboard kind as a
u32 (0 = standard), but the window handler decoded it with
glib::EnumValue::from_value, which always returns None for a u32. The
"standard clipboard" check therefore always failed and no
"Copied to clipboard" / "Cleared clipboard" toast was ever shown
(app-notifications = clipboard-copy), neither for keybind copies nor for
OSC 52 writes. The handler now takes the u32 directly.
Test Plan:
- run `printf '\e]52;c;aGVsbG8=\a'`: toast appears, pixel-identical to
Ghostty 1.3.1