Ask for a machine that can build an image

Dropping the hanzo-build- prefix widened this job's pool, and the pool it widened
into cannot do the job: the ephemeral runner-github-papers-* runners advertise a
bare linux-amd64 and carry no docker daemon, so the build died on
/var/run/docker.sock: no such file or directory. The run before it, on
evo-amd64, was green. Same workflow, same commit range, different machine.

The old label was not better — it was answered by evo alone, so when evo was off
the network the job queued forever with nothing to read. Both failures are the
same defect wearing different clothes: a label that does not mean what the job
needs.

self-hosted is what separates them, and it is already a documented capability
token rather than a machine's name, so the four names stand. An image build says
it needs a persistent runner; the ephemeral pool keeps the jobs that only need a
checkout and a node.

The real fix is upstream of this file: a runner that cannot build an image should
not advertise the label image builds ask for. Until the ephemeral pool either
gains a daemon or drops the label, this is the line that keeps the build on a
machine that can run it.

Co-authored-by: Hanzo Dev <[email protected]>

.github/workflows/build-papers.yml

@@ -21,7 +21,7 @@ permissions:
 
 jobs:
   build-pdfs:
-    runs-on: linux-amd64
+    runs-on: [self-hosted, linux-amd64]
 
     steps:
       - name: Checkout repository

.github/workflows/deploy-site.yml

@@ -25,7 +25,7 @@ env:
 
 jobs:
   build:
-    runs-on: linux-amd64        # self-hosted arcd (hanzoai org)
+    runs-on: [self-hosted, linux-amd64]        # self-hosted arcd (hanzoai org)
     permissions:
       contents: read
       packages: write