feat(ci): migrate all workflows to GKE self-hosted runners

Swap all `runs-on: ubuntu-latest` to `runs-on: arc-runner-set` all jobs.
The ARM docker build job in docker.yml uses `${{ matrix.runner }}`
and is left untouched since the GKE runner pool is x86_64 only.

Runners are backed by ARC (Actions Runner Controller) on a GKE cluster
with a spot preemptible node pool that scales based on job demand.

Use the baked Electron dependencies for the desktop E2E job.

.github/workflows/deploy-site.yml

@@ -40,7 +40,7 @@ jobs:
     # a skills-index PR that doesn't touch website/** paths and so
     # doesn't auto-deploy via the deploy-docs path.
     if: github.event_name == 'release' || github.event_name == 'workflow_dispatch'
-    runs-on: ubuntu-latest
+    runs-on: arc-runner-set
     timeout-minutes: 30
     steps:
       - name: Trigger Vercel Deploy
@@ -48,7 +48,7 @@ jobs:
 
   deploy-docs:
     if: github.repository == 'NousResearch/hermes-agent'
-    runs-on: ubuntu-latest
+    runs-on: arc-runner-set
     timeout-minutes: 30
     environment:
       name: github-pages