[lavan8t]

Replaces #197 — that PR added a second Windows-only connectivity state machine next to LatchEngine. This one keeps the two pieces that were worth keeping (NCSI's connectivity level, event-driven address-change detection) and feeds them to the shared engine.

What changed

Windows tells the engine when a captive portal appears (WindowsWifiPlatform)

• The Wi-Fi query now also asks WinRT for the connectivity level of the internet profile (NetworkInformation.GetInternetConnectionProfile()): None, LocalAccess, ConstrainedInternetAccess, InternetAccess.
• Only a WLAN profile counts. On a docked laptop the internet profile is Ethernet, and its level says nothing about the Wi-Fi link, so it is dropped rather than read as the Wi-Fi's own.
• When Windows moves the level into ConstrainedInternetAccess, the platform emits the new WifiEvent.Changed. The engine handles it exactly as it handles WifiEvent.Available: the same probe, the same campus-SSID and Pronto gate, the same autoLogin setting. Nothing about the credential path changes.
• A level that flaps is damped — one report per 30 s.

The Wi-Fi loop wakes on the OS instead of only on its timer (WindowsIpChangeNotifier)

• iphlpapi's NotifyAddrChange is registered asynchronously with an OVERLAPPED of our own, so it can be given back with CancelIPChangeNotify when the app stops. A blocking call cannot be cancelled and keeps triggering checks after stop().
• The handle Windows hands back is left alone — the documentation says not to close it, because Windows shares it.
• Off Windows the notifier does nothing and the poll loop carries on exactly as before.

The shared engine (LatchEngine)

• One new case in the Wi-Fi event handling: WifiEvent.Changed → re-check. No new states, no second coordinator, no second login path.

What is deliberately not here

• The parallel WindowsHostelConnectivityMonitor / HostelAuthenticator / HostelConnectivityState and the CaptivePortalDetector rewrite from [Windows]: Implement automatic hostel Wi-Fi authentication and connectivity recovery #197. They duplicated the engine's recovery and login logic, ignored autoLogin and the latch state, could deadlock on the non-reentrant mutex, and would have dropped the Pronto gate ([Fix]: Send portal credentials only when the portal points at Pronto #210) and the Base64 Wi-Fi fields ([Fix]: Keep Windows Wi-Fi names from shifting other fields #223).
• The latency / DEGRADED tracking from [Windows]: Implement automatic hostel Wi-Fi authentication and connectivity recovery #197: nothing consumes it yet.

Verification

• ./gradlew :core:desktopTest — green, including the new tests
• ./gradlew :desktop:compileKotlinDesktop :cli:build :cli:test :desktop:smoke — green
• ./gradlew assembleDebug testDebugUnitTest :app:lintDebug — green

Needs a run on Windows

The native path and the WinRT query only exist on Windows, and CI here is Linux, so this still needs a run on a real Windows machine: the NCSI level, the NotifyAddrChange wake-up, and the Changed event reaching the engine.