`SendService`/`RecvService` took a raw `WakuNode` and reached into its
internals (`wakuStoreClient`, `subscriptionManager`, `peerManager`),
which breaks the layering: the messaging layer should depend on the Waku
kernel, not the node.
Widen the Waku api surface with the operations these services need
(`storeQueryToAny`, `isStoreMounted`, `hasStorePeer`, `isContentSubscribed`,
`subscribedContentTopics`) and switch both services to hold `Waku` and
call that surface instead. The send-processor chain still pulls raw
publish handles (relay/lightpush/RLN/peer manager) from `waku.node`,
since the kernel API does not expose publishing primitives yet; this is
isolated to the constructor and flagged with a comment.
Also make `MessagingClient.new` return explicitly.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The messaging api layer reached around the Waku kernel into the libp2p
node (`waku.node.subscriptionManager`, `waku.node.rng`,
`waku.node.brokerCtx`). That breaks the declared layering: messaging
depends on the Waku *kernel* abstraction, not the raw node.
Add a content-topic subscription api on the Waku layer
(`waku/api/subscriptions.nim`) and switch the messaging send/subscription
paths onto it, plus the kernel's own `rng`/`brokerCtx` fields, so the
layer no longer touches `node` internals.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
