Function createDefaultMessaging

createDefaultMessaging(options: DefaultMessagingOptions): MessagingRegistry
The shell's messaging registry with kernl's four providers registered and preferences persisted at kernl:messaging:v1.

createKernl passes the account-signer backends for all four providers and the active account's signer, so each follows the account: sign-in-required while nobody is signed in, signer-cannot-encrypt while the signer lacks the encryption the format needs. A provider given no backend stays unavailable: no-runtime for ratchet and group, sign-in-required for the others. The shell describes, it does not pretend.
Parameters
- options: DefaultMessagingOptions
  Storage, backend constructors and the active signer.
Returns MessagingRegistry
A MessagingRegistry.
Example
```
const messaging = createDefaultMessaging({ storage: localStorage });
messaging.get('private')?.availability; // { available: false, reason: 'sign-in-required' }
messaging.get('ratchet')?.availability; // { available: false, reason: 'no-runtime' }
messaging.get('group')?.availability; // { available: false, reason: 'no-runtime' }
```