`declare` sends a node a signed declaration; `serve` now also consumes reports.
Signed over the exact bytes published, which is what the node verifies. Anything
re-encoding in between would sign one thing and check another, and a difference
in key order alone would have a node refuse a declaration that was genuinely
the mesh's.
Sent to the node's queue directly rather than through the exchange: a
declaration is for one node, and routing by name through a shared exchange
means a binding per node that nothing removes when a node is retired.
Enrolment now issues the node its own broker password, replacing the token's
secret, and tells it the broker address, the fingerprint and the signing key --
so a node can reconnect after a restart without a person and a new token, which
is what makes disconnection ordinary rather than a crisis.
A report is a statement, not a write. What a node says it applied is its own
account of its own machine, kept as a copy for recovery rather than as a source.
