Function check

check(state: AclState, identity: Identity, cap: number): boolean
Check whether an identity has a specific capability.

Decision logic:
1. If identity has no entry: return based on defaultPolicy
  - 'permissive' → true (all caps granted to unknown identities)
  - 'restrictive' → false (all caps denied to unknown identities)
2. If identity is blocked: return false (blocked overrides all caps)
3. Otherwise: return (entry.caps & cap) !== 0
Parameters
- state: AclState
  Current ACL state (immutable)
- identity: Identity
  Napplet identity to check
- cap: number
  Capability bit constant (e.g., CAP_RELAY_READ)
Returns boolean
true if the identity has the capability, false otherwise
Example
```
import { check, createState, grant } from '@kehto/acl';
import { CAP_RELAY_READ } from '@kehto/acl';

const state = createState('restrictive');
const id = { dTag: 'chat', hash: 'ff00' };

check(state, id, CAP_RELAY_READ); // false (restrictive, no entry)

const state2 = grant(state, id, CAP_RELAY_READ);
check(state2, id, CAP_RELAY_READ); // true
```
- Defined in check.ts:57