Name the appliance check for what it proves

.github/workflows/tests.yml

@@ -30,13 +30,20 @@ jobs:
     # https://mirror.keellinux.org/layers, verified, assembled into a scratch
     # rootfs, booted in LXC and checked by tests/boot-test.sh. Nothing is built
     # there; the build host publishes the layer (docs/releases-host.md of the
-    # keel repository).
+    # keel repository). So what boots is the layer the mirror publishes, never
+    # this branch: a pull request that changes the recipe is not exercised by
+    # this check, which is why the reusable job is called
+    # boot-published-layer.
     #
     # test-appliance.yml targets the labels "self-hosted, keel-lxc"; a job aimed
     # at a label no runner carries stays queued until GitHub cancels it after 24
     # hours, so the reusable workflow's contract is that callers gate on the
     # organization variable KEEL_LXC_RUNNER (docs/ci-cd.md section 5 of the keel
-    # repository). This job produces the check "appliance / build-and-boot".
+    # repository). A layer that has never been published fails this job
+    # instead of passing it; the bootstrap exemption for a repository whose
+    # first layer does not exist yet is allow_unpublished, and this layer is
+    # published, so it is not used here. This job produces the check
+    # "appliance / boot-published-layer".
     if: vars.KEEL_LXC_RUNNER == 'true'
     uses: keel-linux/.github/.github/workflows/test-appliance.yml@main
     with:

COVERAGE.md

@@ -74,11 +74,15 @@ never what it was.
 
 ## The appliance gate
 
-`appliance / build-and-boot` runs through the organization's
+`appliance / boot-published-layer` runs through the organization's
 `test-appliance.yml` on the self-hosted `keel-lxc` runner, which fetches the
 published layer from `https://mirror.keellinux.org/layers`, verifies it,
 assembles it, boots it in LXC and runs `tests/boot-test.sh`. Nothing is built
-there.
+there, so what boots is the published layer and not this branch: a pull request
+that changes the recipe is not exercised by this check, which is why the job is
+`boot-published-layer` and not the old `build-and-boot`. A layer that has never
+been published fails it rather than passing it (keel-linux/.github pull request
+12).
 
 ### What the boot test proved against the published layer, 2026-09-27
 
@@ -168,7 +172,7 @@ never reached a machine, which is the trap docs/traps.md records:
 ## Plan
 
 - Require `tests / coverage`, `package / changelog` and
-  `appliance / build-and-boot` on `master`.
+  `appliance / boot-published-layer` on `master`.
 - Rebuild on the `apache-php` layer when it lands, which changes the parent and
   the digest and nothing else here.
 - Measure `conf.d/main`. A build time script that runs inside a chroot as root