Convert the SettingsModal.general 'saves X via settings payload' tests from
real-timer waitFor (each burning a real ~500ms auto-save debounce) to the
FN-7506 fake-timer pattern already used by the auto-save tests in this file.
Payload-routing/coalescing assertions are unchanged; only the artificial
wall-clock wait is removed (Standing Rule: prefer fake timers over real time
waits). Isolated test-execution time drops ~21.7s -> ~15.0s (82 tests, all
green across repeated runs).
a1b56f11e3