ci: run linux jobs on hanzo-build-linux-amd64 ARC scale set (no GitHub-hosted builders)

Claude-Session: https://claude.ai/code/session_01RFrWpXc1BsqfrFYMbyDusJ

.github/workflows/ci.yaml

@@ -12,7 +12,7 @@ permissions:
 jobs:
   build:
     name: build & test
-    runs-on: ubuntu-latest
+    runs-on: hanzo-build-linux-amd64
     env:
       GOPRIVATE: github.com/hanzoai/*
       GOSUMDB: "off"

.github/workflows/docker-site.yaml

@@ -26,7 +26,7 @@ concurrency:
 jobs:
   build-push:
     name: build & push o11y-site image
-    runs-on: ubuntu-latest
+    runs-on: hanzo-build-linux-amd64
     steps:
       - name: Checkout
         uses: actions/checkout@v4

.github/workflows/docker.yaml

@@ -16,7 +16,7 @@ concurrency:
 jobs:
   build-push:
     name: build & push image
-    runs-on: ubuntu-latest
+    runs-on: hanzo-build-linux-amd64
     steps:
       - name: Checkout
         uses: actions/checkout@v4

.github/workflows/release-drafter.yml

@@ -18,7 +18,7 @@ jobs:
       # write permission is required for autolabeler
       # otherwise, read permission is required at least
       pull-requests: write
-    runs-on: ubuntu-latest
+    runs-on: hanzo-build-linux-amd64
     steps:
       # (Optional) GitHub Enterprise requires GHE_HOST variable set
       #- name: Set GHE_HOST