Capability Negotiation

Kehto uses two complementary capability checks:

1. The NIP-5A manifest declares required NAPs through requires.
2. Hosted napplets call window.napplet.shell.supports() to check host capabilities at runtime.

Required capabilities should fail early at load time when unsupported. Optional capabilities should degrade gracefully inside the napplet.

Do not rely on static helper-package knowledge as the hosted contract. The shell should answer from the capabilities it actually provides.