fix(server): wrap awareness origin as TransactionOrigin

[dschmidt]

Problem

onAwarenessUpdate({ connection }) is always undefined in v4. The awareness listener in Hocuspocus.ts reads it via isTransactionOrigin(origin), but the producers (MessageReceiver awareness branch and Document.applyAwarenessUpdate) pass the raw Connection. The type guard returns false, so the connection is never forwarded to the hook and server-side awareness work that depends on the per-update authenticated user cannot function.

Fix

Wrap origin as { source: 'connection', connection } at the producer sites, matching the sync handlers in the same MessageReceiver. Update Document.handleAwarenessUpdate to extract the connection through the existing type guard. Tighten the related parameter types with satisfies ConnectionTransactionOrigin and TransactionOrigin | null so future producers cannot regress.

I suspect this matches the original v4 intent: Hocuspocus.ts's awareness listener was already written for TransactionOrigin, the sync handlers already wrap, and the previous originConnection: Connection | null parameter on handleAwarenessUpdate looks like a leftover pre-v4 signature. The y-protocols origin: any typing hid the inconsistency from the compiler.

Soft API break

Listeners attached directly via document.awareness.on('update', ...) now receive a TransactionOrigin (or { source: 'local' } for non-connection origins) instead of a raw Connection. Migration:

const conn = isTransactionOrigin(origin) && origin.source === 'connection'
  ? origin.connection
  : null

The supported onAwarenessUpdate hook is unaffected and gains the resolved payload.connection.

Alternative

If full backwards compatibility is preferred, I can instead make the consumer side tolerant of both raw Connection and wrapped TransactionOrigin, leaving the producers untouched. Happy to switch.