Name the one genesis bundle in every bed and the README (hq issue 146, ADR 0331)

mesh-host now carries one genesis bundle, foundation-first-node.lock, on the bus the
mesh runs on; the NATS one it replaces is deleted. Beds that still named it would point
at a file that is gone, and the harness's rewrite for the previous broker's image
rewrote nothing.

test/integration/route-forwarding.test.ts

@@ -25,7 +25,7 @@
  * publicly-trusted certificate and answering an HTTP-01 challenge at the name — is proven separately
  * by certificates.test.ts, which drives the same proxy binary against a real ACME server (Pebble).
  *
- *   MESH_LAB_HOST_BINARY=.../mesh-host   MESH_LAB_BUNDLE=.../examples/foundation-first-node-nats.lock
+ *   MESH_LAB_HOST_BINARY=.../mesh-host   MESH_LAB_BUNDLE=.../examples/foundation-first-node.lock
  *   scripts/build-route-proxy-image.sh builds mesh-route-proxy:development into the local daemon;
  *   scenarios/route-forwarding.yml stocks it and alpine:latest, and serves both by digest.
  */