Simplify default target examples

[SandroMaglione]

Summary

• simplify empty and default-constructible transition targets across the example applications
• document bare target selections as the type-safe equivalent of zero-argument target.from()
• retain explicit resolvers for transitions that consume context, construct data, enqueue commands, or request reentry

Changeset

• Added or updated for a library or package-metadata change
• Not required because this PR does not change src/ or package.json

Validation

• pnpm check
• Relevant example checks, when examples changed
• Automated type-performance measurement passed or was not required
• Automated runtime- and memory-performance measurement passed or was not required

Example checks:

• examples/platformer: pnpm check
• examples/playground: pnpm check
• examples/pokemon: pnpm check