test(hooks): pin _connected_device on MacOSThumbButtonTests for TomBadash#185 integration

``MacOSThumbButtonTests._make_hook`` previously left
``hook._connected_device`` unset. The thumb-button dispatch path runs
unconditionally on this branch, so the test passes; but TomBadash#185 adds an
early-return at the top of the CGEventTap callback gated on
``_should_intercept_events`` (which is ``self._connected_device is not
None``), and once both PRs are integrated that gate fires before
``btn=6`` reaches the thumb-button handler and the assertions about
``THUMB_BUTTON_DOWN`` / ``THUMB_BUTTON_UP`` / ``XBUTTON1_DOWN`` start
failing.

Pin a stub ``SimpleNamespace`` device on the hook in ``_make_hook``.
This is also semantically more truthful: btn=6 / btn=3 only originate
from a connected MX Master mouse in production, so the test should
model that state rather than the "no Logitech bound" cold-start state
the dispatch path was never designed for.

No-op against current master (the early-return does not yet exist);
becomes load-bearing as soon as TomBadash#185 lands.

Author: hughesyadaddy

tests/test_mouse_hook.py

@@ -909,6 +909,20 @@ def _make_hook(self):
         hook._running = True
         hook._tap = MagicMock(name="tap")
         hook._enqueue_dispatch_event = MagicMock(name="enqueue")
+        # Pin a stub ``_connected_device`` so this test class stays
+        # truthful (btn=6 / btn=3 only originate from a connected MX
+        # Master in production) and so it composes with the top-level
+        # ``_should_intercept_events`` early-return that lands in
+        # #185 (``fix(hooks): pass through OS mouse events when no
+        # Logitech is connected``). On this branch the gate is not yet
+        # consulted at the top of the CGEventTap callback, so this is a
+        # no-op against current master; it becomes load-bearing once
+        # #185 is integrated.
+        hook._connected_device = SimpleNamespace(
+            key="mx_master_4",
+            thumb_button_via_hid=False,
+            gesture_via_sense_panel=False,
+        )
         return hook
 
     def _mock_field(self, button_number):