React Native standalone: Metro orphaned — shared session factory never calls launcher.onComplete()

Standalone mode only (driving the service outside the WDIO testrunner via createMobileSession; normal testrunner runs are fine because WDIO calls onComplete itself).

The shared factory packages/native-mobile-core/src/session.ts never references onComplete: its MobileLauncherLike contract declares only onPrepare, and cleanup() calls service.after() + browser.deleteSession() but never launcher.onComplete(). React Native's launcher owns Metro (packages/react-native-service/src/launcher.ts #metro, started in onPrepare under manageMetro), stopped only in onComplete() → #stopMetro().

Result: with manageMetro, Metro (port 8081) is orphaned on cleanup() and on remote()/before() startup failure — a superset of the tauri standalone bug (#636), since it also leaks on the happy path.

Fix (in native-mobile-core): add onComplete to MobileLauncherLike and call it — guarded so it can't mask the original error (ideally surfaced via AggregateError) — in the remote()-failure path, the service.before()-failure path, and in cleanup(). No-ops safely for Flutter (its launcher spawns nothing).

Related: #636 (the tauri fix this mirrors), #445 (standalone coverage/contract).

Start in packages/native-mobile-core/src/session.ts and compare the MobileLauncherLike contract and cleanup(), remote(), and service.before() failure paths with packages/react-native-service/src/launcher.ts, especially Metro startup and onComplete(). Ensure launcher completion is invoked safely on all specified paths without masking the original error, then add or update standalone coverage referenced by #445.