ci(e2e): install with pnpm 11, matching the version developers run

.github/workflows/ci.yml

@@ -243,7 +243,11 @@ jobs:
           node-version: 20
       - uses: pnpm/action-setup@v6
         with:
-          version: 9
+          # Matches the pnpm developers run locally. The harness's
+          # `tests/e2e/pnpm-workspace.yaml` uses the `allowBuilds` key this
+          # line unlocks — pnpm 9 rejects that file outright, so the two
+          # must move together.
+          version: 11
       - name: check harness exists
         id: harness
         run: |

tests/e2e/pnpm-workspace.yaml

@@ -0,0 +1,11 @@
+# pnpm 10+ does not run a dependency's install scripts unless it is named
+# here. esbuild (via vitest) links its platform binary in that script, and
+# pnpm 9 ran it by default — so keeping it enabled preserves the behavior
+# this harness has always had. Without the entry `pnpm install` fails with
+# ERR_PNPM_IGNORED_BUILDS.
+#
+# This file MUST NOT be committed while CI still installs with pnpm 9: a
+# workspace manifest without a `packages:` key fails that version outright
+# ("packages field missing or empty").
+allowBuilds:
+  esbuild: true