fix(mouse-enhancer): middle-click stops working after app restart

[ayangweb]

fixed #202

After each app or system restart, the simulate-middle-click feature is silently broken until the user toggles its switch off and back on.

Two defects in MouseEnhancerMiddleClickSession:

1. CGEvent tap not re-enabled when macOS auto-disables it

macOS can send tapDisabledByTimeout / tapDisabledByUserInput to a non-listen cghidEventTap during busy startup or after sleep. The tap callback did not handle these events, so the tap stayed disabled permanently. MouseEnhancerSession (scroll reversing) already has this recovery; add the same to the middle-click session:

if type == .tapDisabledByTimeout || type == .tapDisabledByUserInput {
    if let tap = session.eventTap, CFMachPortIsValid(tap) {
        CGEvent.tapEnable(tap: tap, enable: true)
    }
    return passthrough
}

2. MTDeviceCreateList returns empty at login-item startup

When the app launches as a login item at boot, MultitouchSupport.framework may not have finished enumerating devices yet, so _mtDeviceCreateList() returns an empty array and no touch listeners are registered. The existing IOKit kIOFirstMatchNotification recovery does not help here—it drains currently-present devices on registration (arming future arrivals) but never fires a callback for devices already in the IOKit registry. Result: no touch data, threeDown never set, middle-click silently dead.

Schedule a one-shot 3-second rebuild at the end of start() when no devices are found, mirroring the existing wake-restart recovery:

if devices.isEmpty {
    scheduleRestart(after: 3, reason: "noDevicesAtStart")
}

Tests

Added testMiddleClickStartsOnActivateWhenSavedAsEnabledAndAccessibilityGranted and testMiddleClickDoesNotStartOnActivateWhenAccessibilityDenied to cover the activate() path (app-restart scenario) with pre-persisted settings, which had no test coverage.

[ayangweb]

@ggbond268 copilot 修复的，需要你来测试