fix: add corepack install step to make pnpm available

Author: renderffx

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
         with:
           node-version: ${{ env.NODE_VERSION }}
           cache: pnpm
-      - run: corepack enable && pnpm install --frozen-lockfile
+      - run: corepack enable && corepack install && pnpm install --frozen-lockfile
       - run: pnpm run typecheck
 
   test:
@@ -29,7 +29,7 @@ jobs:
         with:
           node-version: ${{ env.NODE_VERSION }}
           cache: pnpm
-      - run: corepack enable && pnpm install --frozen-lockfile
+      - run: corepack enable && corepack install && pnpm install --frozen-lockfile
       - run: pnpm run test:ci
 
   benchmark:
@@ -41,7 +41,7 @@ jobs:
         with:
           node-version: ${{ env.NODE_VERSION }}
           cache: pnpm
-      - run: corepack enable && pnpm install --frozen-lockfile
+      - run: corepack enable && corepack install && pnpm install --frozen-lockfile
       - run: pnpm exec tsx bench/engine-bench.mts
         name: Engine Performance Benchmark (regression detection)
 
@@ -54,5 +54,5 @@ jobs:
         with:
           node-version: ${{ env.NODE_VERSION }}
           cache: pnpm
-      - run: corepack enable && pnpm install --frozen-lockfile
+      - run: corepack enable && corepack install && pnpm install --frozen-lockfile
       - run: pnpm run build