The bus is the only broker; step 1 starts

A module does declare requirements the provisioner fulfils — but the broker
it gets that way is a private vhost, the analog of a database, not the
mesh's bus. Two modules of the new mesh depend on it, so the compatibility
broker was never single-purpose and its retirement would have stranded them.

NATS is the heart: one bus, a module's messaging is subjects on it scoped by
what it declares, and no module is handed a server of its own. The seat
delivers nothing; the interface retires with the broker. Also closes the
EVENTS question — one stream, on the bootstrap argument, not preference.

Designs 25 and 28 go in-progress: step 1 is starting.

The insight check caught a false positive on its own first real use — its
bold-run pattern crossed newlines and joined an unrelated `**` to the
marker. Constrained to one line, still catching all four bad shapes.

02-DECISIONS/0106-the-bus-is-nats.md

@@ -75,6 +75,19 @@ after its deliveries are exhausted; a module's account cannot publish outside it
 subscribe outside its `consumes`. Then the cutover bed: a mesh on AMQP with the predecessor's
 compatibility broker beside it moves its bus in one rollout with every node reporting afterwards.
 
+## Progressive insight
+
+> **Progressive insight — 2026-09-26.** *The compatibility broker was not single-purpose when this
+> was written.* This record says the adopted AMQP broker is "kept as a module with one purpose —
+> the predecessor's clients". Two modules of the new mesh also depended on it, through a `requires:
+> ["amqp"]` grant its provisioner answered with a private vhost — `amqp-ping` and
+> `amqp-email-forwarder`. On the retirement condition below, both would have been left requiring
+> something no provider answers.
+> [ADR 0117](0117-the-bus-is-the-only-broker.md) resolves it by moving them onto the bus and
+> retiring the interface, which makes this record's sentence true rather than merely intended. The
+> decision — the bus is NATS, the AMQP broker becomes the predecessor's compatibility broker and
+> retires with the last of them — is unchanged.
+
 ## References
 
 - [research 014](../01-RESEARCH/014-the-bus-on-nats/00-overview.md)