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

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

.github/workflows/ci.yml

@@ -17,7 +17,7 @@ env:
 jobs:
   test-contracts:
     name: Test Smart Contracts
-    runs-on: ubuntu-latest
+    runs-on: lux-build-amd64
     steps:
     - uses: actions/checkout@v4
     - name: Setup Node.js
@@ -34,7 +34,7 @@ jobs:
       run: pnpm test
   test-frontend:
     name: Test Frontend
-    runs-on: ubuntu-latest
+    runs-on: lux-build-amd64
     steps:
     - uses: actions/checkout@v4
     - name: Setup Node.js
@@ -57,7 +57,7 @@ jobs:
       run: pnpm test || true
   test-api:
     name: Test API
-    runs-on: ubuntu-latest
+    runs-on: lux-build-amd64
     steps:
     - uses: actions/checkout@v4
     - name: Setup Bun
@@ -77,7 +77,7 @@ jobs:
       run: bun test || true
   e2e-tests:
     name: E2E Tests
-    runs-on: ubuntu-latest
+    runs-on: lux-build-amd64
     needs:
     - test-contracts
     - test-frontend
@@ -132,7 +132,7 @@ jobs:
         path: ./stack/playwright-report/
   create-release:
     name: Create Release
-    runs-on: ubuntu-latest
+    runs-on: lux-build-amd64
     if: github.event_name == 'push' && github.ref == 'refs/heads/main'
     permissions:
       contents: write
@@ -156,7 +156,7 @@ jobs:
         prerelease: false
   deploy:
     name: Deploy to Production
-    runs-on: ubuntu-latest
+    runs-on: lux-build-amd64
     needs:
     - create-release
     if: github.event_name == 'release' || (github.event_name == 'push' && github.ref == 'refs/heads/main')