feat(spawn-application): migrate launcher discovery to ServiceLoader

[deer]

• Replaces the custom META-INF properties file parser in AbstractTemplatedPlatform with standard ServiceLoader + JPMS provides/uses wiring, eliminating ~100 lines of brittle classpath-scanning and string-parsing code.
• Introduces LauncherRegistration — a typed service interface that associates a Launcher class with a specific Application and AbstractTemplatedPlatform type; discovered at runtime via ServiceLoader.
• Migrates spawn-local-platform and spawn-local-jdk to the new mechanism with LocalLauncherRegistration and LocalJDKLauncherRegistration records, deleting the corresponding META-INF properties files.
• Fixes raw Launcher types throughout: LauncherRegistration.launcherClass() and the internal launchers map now use Class<? extends Launcher<?, ?>>, removing all @SuppressWarnings("rawtypes") in favour of one targeted @SuppressWarnings("unchecked") at the unavoidable type-erased cast site.