fix(ci): route helper-test tmpdir off the host /tmp tmpfs (#15979)

* fix(ci): route helper-test tmpdir off the host /tmp tmpfs

* test(ci): pin the helper-battery tmpdir routing against comments

Two gaps in the #15979 change:

- The pin used toContain/indexOf on the raw run block, so prefixing the
  export with `# ` disabled the routing while the guard stayed green.
  Filter comment lines before asserting, like the lint-history pin already
  does, and pin the private dir + EXIT trap the step now creates.
- The step routed TMPDIR straight into the shared RUNNER_TEMP root. Copy
  the unit lanes' second half too: mktemp -d under RUNNER_TEMP and reap it
  on EXIT, so a cancelled battery does not leave its fixture tree behind
  (its own after() hook does not run on a signal).

Co-authored-by: Qwen-Coder <[email protected]>
Patrol-Run: qwen-pr-closeout/jmvvyiud548

---------

Co-authored-by: Qwen-Coder <[email protected]>

.github/workflows/ci.yml

@@ -1476,6 +1476,20 @@ jobs:
       - name: 'Run .github/scripts helper tests'
         if: "${{ needs.classify_pr.outputs.skip_ci != 'true' && steps.ci_profile.outputs.ci_profile == 'full' }}"
         run: |-
+          # Route os.tmpdir() off the host /tmp tmpfs: its inode quota is
+          # small and shared across the pool, and e2e-build.test.mjs creates
+          # thousands of chunk files there (#15965 ENOSPC with 202G free).
+          # Same routing as the unit lanes (#10035), private per-run dir
+          # included: RUNNER_TEMP is shared, and a cancelled battery never
+          # reaches its own after() cleanup, so the fixture tree would stick
+          # around in _work/_temp. A hard kill stays uncovered either way.
+          export TMPDIR="${RUNNER_TEMP:-${TMPDIR:-/tmp}}"
+          HELPER_TMPDIR="$(mktemp -d "${TMPDIR}/helper-tests-XXXXXX" 2>/dev/null)" || HELPER_TMPDIR=""
+          if [ -n "$HELPER_TMPDIR" ]; then
+            TMPDIR="$HELPER_TMPDIR"
+            export TMPDIR
+            trap 'rm -rf "$HELPER_TMPDIR"' EXIT
+          fi
           node --test --test-concurrency=1 ${{ env.HELPER_TESTS }} 2>&1 | tee "${RUNNER_TEMP}/helper-attempt1.log" || {
             node --test --test-concurrency=1 ${{ env.HELPER_TESTS }} &&
               echo "::warning::helper tests failed once and the retry absorbed it; attempt-1 failures: $(grep -E '^not ok' "${RUNNER_TEMP}/helper-attempt1.log" | head -5 | paste -sd ';' -) — count this toward the #12772 helper-battery recurrence threshold"

scripts/tests/ci-platform-lanes.test.js

@@ -1258,6 +1258,32 @@ describe('GitHub helper tests', () => {
     }
   });
 
+  it('routes the battery tmpdir off the host /tmp tmpfs', () => {
+    // #15965: e2e-build.test.mjs mkdtemps thousands of chunk files via
+    // os.tmpdir(); on the ECS pool that defaulted to the shared /tmp tmpfs,
+    // whose ~1M inode quota filled up and failed the lane with ENOSPC while
+    // 202G of capacity stayed free. RUNNER_TEMP sits on the roomy data disk,
+    // same routing the unit lanes already use (#10035).
+    const step = (ci.jobs.lint_and_static.steps ?? []).find(
+      (candidate) => candidate.name === 'Run .github/scripts helper tests',
+    );
+    expect(step, 'helper-tests step missing').toBeDefined();
+    // Comments stripped: the rationale above the export names it too, so a pin
+    // satisfied by prose would stay green with the routing commented out.
+    const run = String(step.run)
+      .split('\n')
+      .filter((line) => !line.trim().startsWith('#'))
+      .join('\n');
+    expect(run).toContain('export TMPDIR="${RUNNER_TEMP:-${TMPDIR:-/tmp}}"');
+    expect(run.indexOf('export TMPDIR')).toBeLessThan(
+      run.indexOf('node --test'),
+    );
+    // The routed dir is private to the run and reaped on exit: RUNNER_TEMP
+    // itself is shared with every other job on the host.
+    expect(run).toContain('mktemp -d "${TMPDIR}/helper-tests-XXXXXX"');
+    expect(run).toContain('trap \'rm -rf "$HELPER_TMPDIR"\' EXIT');
+  });
+
   it('retries the full-profile battery once against pool contention', () => {
     // #12772: the battery spawns real subprocess loops on the shared ECS
     // pool, and a push to main has no flaky-rerun patrol — one host hiccup