fix(ci): build app on 16vcpu runner to stop cold-cache OOM kills (#5944)

Author: waleedlatif1

.github/workflows/test-build.yml

@@ -197,11 +197,18 @@ jobs:
   # harmless), but the Turbo cache gets its own key: with a shared key, only
   # the last committer's new entries survive each run, so the test and build
   # Turbo entries would evict each other nondeterministically.
-  # Same next build as the app image, so it needs the same larger runner in
-  # GitHub mode: it peaks ~21.9 GB and SIGKILLs on the free 16 GB ones.
+  # Same next build as the app image, so it needs a large runner. Peak RSS
+  # tracks Turbo/Turbopack cache warmth, and it is the COLD case that sizes the
+  # runner: warm peaks ~12 GB, partial ~28 GB, and a cold full rebuild peaked
+  # 51 GB. The 8vcpu tier only has 30.4 GB, so cold-cache runs OOM-killed the VM
+  # (oom_count 1, memory p100 ~30.5 GB, ~99% of the tier) — the job burned 8-15
+  # min and died, while warm runs finished under 8 min. NODE_OPTIONS'
+  # --max-old-space-size only caps Node's JS heap; the bulk is native Turbopack
+  # worker memory, so the cap cannot prevent this. 16vcpu = 60.8 GB fits the
+  # 51 GB cold peak with headroom. Keep the test job on 8vcpu; its memory is fine.
   build:
     name: Build App
-    runs-on: ${{ (vars.CI_PROVIDER == '' || vars.CI_PROVIDER == 'blacksmith') && 'blacksmith-8vcpu-ubuntu-2404' || 'linux-x64-8-core' }}
+    runs-on: ${{ (vars.CI_PROVIDER == '' || vars.CI_PROVIDER == 'blacksmith') && 'blacksmith-16vcpu-ubuntu-2404' || 'linux-x64-8-core' }}
     timeout-minutes: 15
 
     steps: