forgetest: cloud.service-protocol, the service answered by the emulator in this machine's identity

The service-protocol half of the cloud catalog on its own test: the cloud
client restarted as gfutilities' emulator under the /run/gfcloud-emulate
marker signs in, passes the firmware check, opens the WebSocket, answers
the connect-time hunt and the image requests with the dev image's canned
frames, and runs a print from the app through the real download path to
':completed' - nothing moves, nothing arms, and only the app has to be
driven, by a person or an agent through the prompt API. The real client
is restarted afterward and its hunt waited out. session_live now knows
the emulator's session is not the machine's, so enter_cloud restarts it
rather than reusing it; restart_client is the one restart the offline
and emulator entries share.

The dev image adds python3-gfutilities-emulator (the fixtures, packaged
on their own in meta-openglow); forgefirm-app moves to 12ad3b1 (gfcloud
--emulate). Catalog: 44 tests, 27 auto / 9 operator / 8 live; the new
test covers the gfutilities service layer and examples/, which step 4
will take off the other cloud tests. Replays over the prompt script;
contract and BRINGUP updated. A layer change (the dev image recipe):
everything re-requires on the next image.

meta-forgefirm/recipes-forgefirm/images/forgefirm-image-dev.bb

@@ -5,10 +5,12 @@ DESCRIPTION = "OpenGlow/ForgeFIRM development image for Glowforge"
 # Strict superset of forgefirm-image: everything the main image ships, plus
 # debug tooling. forgetest is the release acceptance tool (HTTP :8090) and
 # the bench diagnostics page; it belongs to the bench, never to a release
-# image (docs/ACCEPTANCE.md).
+# image (docs/ACCEPTANCE.md). The gfutilities emulator fixtures are the
+# canned frames its service-protocol test answers the service with.
 IMAGE_INSTALL += " \
   forgectrl \
   forgetest \
+  python3-gfutilities-emulator \
   htop \
 "