ci: migrate runner from lux-build to hanzo-build/hanzo-deploy (ARC consolidation) (#5)

Consolidating to single canonical ARC fleet. Killing duplicate lux-build
scale set. Build job → hanzo-build-linux-amd64 (max 30 on DO). Deploy
job → hanzo-deploy-linux-amd64 (max 20 on DO, correct runner class for
kubectl deploys).

No behavior change for this workflow.

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

.github/workflows/build-lux.yml

@@ -25,7 +25,7 @@ env:
 
 jobs:
   build:
-    runs-on: lux-build-linux-amd64
+    runs-on: hanzo-build-linux-amd64
     permissions:
       contents: read
       packages: write
@@ -74,7 +74,7 @@ jobs:
   deploy:
     needs: build
     if: github.ref == 'refs/heads/main' && github.event_name != 'pull_request'
-    runs-on: lux-build-linux-amd64
+    runs-on: hanzo-deploy-linux-amd64
     permissions:
       contents: read
     steps: