Prepare server template assembly alongside qualification (#31422)

* Prepare template assembly during qualification and cache Intel downloads

* Limit early template qualification polling to fifteen seconds

* Verify Windows retains its download cache policy

* Drop Intel store restoration after measuring its overhead

.github/workflows/node-server-tests.yml

@@ -563,12 +563,11 @@ jobs:
 
   # Design D2: the desktop ships every target's addons, merged from the lanes that qualified them.
   desktop_template:
-    needs: [persistence, mobile_web_bundle, linux_glibc_floor, linux_glibc217_compat, linux_musl]
-    if: >-
-      ${{ !cancelled() && inputs.build_template &&
-      needs.persistence.result == 'success' && needs.mobile_web_bundle.result == 'success' &&
-      needs.linux_glibc_floor.result == 'success' &&
-      needs.linux_glibc217_compat.result == 'success' && needs.linux_musl.result == 'success' }}
+    needs: changes
+    if: ${{ !cancelled() && inputs.build_template }}
+    permissions:
+      contents: read
+      actions: read
     runs-on: ${{ inputs.fast_runners && 'blacksmith-4vcpu-ubuntu-2404' || 'ubuntu-latest' }}
     timeout-minutes: 30
     steps:
@@ -577,6 +576,45 @@ jobs:
           ref: ${{ inputs.ref }}
           persist-credentials: false
       - uses: ./.github/actions/install-node-dependencies
+      - name: Wait for every template qualification lane
+        uses: actions/github-script@v8
+        with:
+          script: |
+            const deadline = Date.now() + 25 * 60_000
+            const expected = {
+              persistence: 6,
+              mobile_web_bundle: 1,
+              linux_glibc_floor: 2,
+              linux_glibc217_compat: 1,
+              linux_musl: 2
+            }
+            while (Date.now() < deadline) {
+              const jobs = await github.paginate(github.rest.actions.listJobsForWorkflowRun, {
+                ...context.repo, run_id: context.runId, filter: 'latest', per_page: 100
+              })
+              const assemblers = jobs.filter(job =>
+                job.name === 'desktop_template' || job.name.endsWith(' / desktop_template'))
+              if (assemblers.length > 1) throw new Error('Ambiguous desktop template qualification')
+              if (assemblers.length === 1) {
+                const prefix = assemblers[0].name.slice(0, -'desktop_template'.length)
+                let ready = true
+                for (const [name, count] of Object.entries(expected)) {
+                  const lanes = jobs.filter(job => job.name === `${prefix}${name}` ||
+                    job.name.startsWith(`${prefix}${name} (`))
+                  if (lanes.length > count) throw new Error(`Unexpected qualification lanes: ${name}`)
+                  for (const lane of lanes) {
+                    if (lane.status === 'completed' && lane.conclusion !== 'success') {
+                      throw new Error(`Template qualification did not succeed: ${lane.name} (${lane.conclusion})`)
+                    }
+                  }
+                  if (lanes.length !== count || lanes.some(lane => lane.status !== 'completed')) ready = false
+                }
+                if (ready) return
+              }
+              await new Promise(resolve => setTimeout(resolve, 15_000))
+            }
+            throw new Error('Timed out waiting for every template qualification lane')
+
       - name: Collect every lane's slot
         uses: actions/download-artifact@v8
         with: