ci: probe the shared harness SDK build cache across runner operating systems

Author: iscekic

.github/workflows/harness-sdk-cache-probe.yml

@@ -0,0 +1,69 @@
+name: harness SDK cache probe
+
+# Temporary: proves that a macos-26 consumer of the harness SDK build restores
+# the entry an ubuntu job saved for the same input hash. Deleted after the run.
+
+on:
+  push:
+    branches: [drain/harness-sdk-cache-probe]
+
+permissions:
+  contents: read
+
+jobs:
+  build-on-linux:
+    runs-on: ubuntu-latest
+    timeout-minutes: 40
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          lfs: true
+
+      - name: Setup pnpm
+        uses: pnpm/action-setup@fc06bc1257f339d1d5d8b3a19a8cae5388b55320 # v4.4.0
+
+      - name: Setup Node
+        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6.3.0
+        with:
+          node-version-file: '.nvmrc'
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Report the build key
+        run: node scripts/harness-sdk-build-key.mjs
+
+      - name: Restore or build the harness SDK
+        uses: ./.github/actions/harness-sdk-build
+
+      - name: Report the dist entry
+        run: ls -d packages/harness-sdk/dist/index.js packages/harness-sdk/dist/index.d.ts
+
+  restore-on-macos:
+    needs: build-on-linux
+    runs-on: macos-26
+    timeout-minutes: 40
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          lfs: true
+
+      - name: Setup pnpm
+        uses: pnpm/action-setup@fc06bc1257f339d1d5d8b3a19a8cae5388b55320 # v4.4.0
+
+      - name: Setup Node
+        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6.3.0
+        with:
+          node-version-file: '.nvmrc'
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Report the build key
+        run: node scripts/harness-sdk-build-key.mjs
+
+      - name: Restore or build the harness SDK
+        uses: ./.github/actions/harness-sdk-build
+
+      - name: Report the dist entry
+        run: ls -d packages/harness-sdk/dist/index.js packages/harness-sdk/dist/index.d.ts