The outbound half went behind `Bus` and a node's two statements stopped naming a
transport. This is the other half, and where the transport reached furthest: the
run loop selected on a channel of the client library's own delivery type, so
every part of holding a node in its mesh knew which bus it was on.
`Link` is dialling, hearing and saying in one interface, because dialling is
where the transport is chosen and choosing it twice is how one half of a node
ends up on a different bus from the other. `Declaration` has one way of being
done rather than two: a declaration set aside for a newer one is settled exactly
as an applied one is, on both buses, and the difference is a fact the report
carries.
Four things this settled.
**The host declares nothing on the new bus.** On the bus the mesh has it declares
its own queue, because a queue that is not there means a node that hears
nothing. Here it binds to a consumer the mesh made when the node enrolled, and a
missing one is said as the mesh's to answer rather than quietly created with
whatever this client happens to default to.
**The pin is easier here than in the tool runtime, not harder.** The Go client
takes a *tls.Config, so the same PinnedConfig with the same VerifyPeerCertificate
does the work — the subject-alternative-name constraint recorded against the
runtime's client is that client's, because it takes PEM strings with no verify
hook. A host checks the fingerprint and nothing else.
**Binding needs the subject as well as the consumer.** An empty subject is
refused rather than taken to mean "whatever that consumer delivers", which the
server said plainly and only when asked.
**Reconnection stays the caller's.** Hold already decides when to try again and
how long to wait; a client reconnecting underneath it would make that reasoning
a duplicate of the library's.
The drain keeps its live half and loses its catch-up half, as it said it would:
verified that three declarations pushed to an absent node leave one on the
stream, and it is the newest.
One test-harness lesson worth the comment it got: delete-then-add is not a reset.
A test that did that inherited the previous test's messages, and the symptom was
a declaration counted as delivered twice — which reads as a redelivery bug in the
code under test rather than as a dirty stream.
