feat(library): call the button Wake Host and tell a sleeping host from one with Polaris down

[papi-ux]

Summary

• The library's Start Polaris button is now Wake Host, which is all a client can do for a host it cannot reach. It cannot start Polaris on a machine that is already awake, and it used to pretend otherwise: wake nothing, wait thirty seconds, then say Polaris did not come online.
• Before waking, the coordinator asks the machine itself. A TCP connect to the streaming port is refused within milliseconds by an awake host with nothing listening and answered by nothing on a sleeping one. The awake case is not woken and is reported within about ten seconds as "The host is awake, but Polaris is not answering. Start it on the host, or enable headless boot so it starts on its own." The silent case still gets the wake packet and the full boot budget, and its timeout message says a wake packet only reaches a sleeping host from its own network, which is what a phone on the road runs into.
• A host that quit since the list last polled is re-polled instead of being blamed for its library for thirty seconds.
• The probe tries every address Nova knows for the host, so a VPN or manual entry is not misread as asleep because the LAN address is out of reach.
• Pairs with fix(packaging): start the user service from the application menu instead of a second process polaris#617 (the application menu starts the user service instead of a second process) and headless boot on the host. Together they make the awake-but-down state rare, and this PR makes the button honest when it happens.

Exact candidate

• Commit: de14895
• Tree: 041beb80edacbabf644d59146505ab4178d6ae55
• Parent: 90ac578
• Base: 90ac578 (master)

Verification

• :app:testNonRoot_gameDebugUnitTest (x86_64): 1615 tests, 0 failures, 0 errors (PolarisStartupCoordinatorTest 10, WakeHostSourceGuardTest 2)
• :app:lintNonRoot_gameDebug -PlintFailOnError=true: clean
• :app:assembleNonRoot_gameDebug (arm64-v8a), installed on the Retroid Pocket 6 as com.papi.nova.debug
• Device: the sidebar button reads Wake Host. With polaris.service stopped on pc-papi and no stream live, pressing it produced the awake-but-down message about 8 s after the press (screenshot); after starting the service, pressing it again opened the library within 3 s.
• Unit tests pin that the awake case sends no wake packet and polls four times, that a silent host still gets the packet and times out, and that a host which went down since the last poll is reported as Polaris not running.

Not covered

• The sleeping-host path (wake packet, timeout message) was not exercised on a device; pc-papi did not sleep today. The unit tests cover the branch.
• androidTest is not compiled by CI and already fails to compile on master; nothing there was touched.