feat: cache the lockfile verification log regardless of cache

The log is under a kilobyte and pnpm writes it on every install, not only
where supply-chain policies are configured: the integrity and tarball-URL
checks are unconditional. A job that starts without it re-checks every
lockfile entry against the registry — on a ~2000-entry lockfile with a warm
store, 13.5s vs 1.5s with `minimumReleaseAge` and `trustPolicy` configured,
and still 6.7s vs 1.6s with no policies at all.

Tying that to the `cache` input made the common case slow for no saving worth
counting, so the log is now restored and saved on its own key whether or not
the store is cached. `cache` goes back to meaning what its name says.

.github/workflows/test.yaml

@@ -334,14 +334,24 @@ jobs:
     # The action caches pnpm's lockfile verification log, which lives in
     # `cacheDir` — a directory pnpm resolves per platform and does not print.
     # Guard the action's copy of that default against pnpm's own.
-    name: 'Lockfile verification cache (${{ matrix.os }})'
+    name: 'Lockfile verification cache (${{ matrix.os }}, cache=${{ matrix.cache }})'
 
     runs-on: ${{ matrix.os }}
 
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, macos-latest, windows-latest]
+        include:
+          # The log is cached independently of the store, so the store-less
+          # configuration has to reach it too.
+          - os: ubuntu-latest
+            cache: false
+          - os: ubuntu-latest
+            cache: true
+          - os: macos-latest
+            cache: true
+          - os: windows-latest
+            cache: true
 
     steps:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
@@ -357,7 +367,7 @@ jobs:
       - uses: ./
         with:
           version: '12.0.0-rc.4'
-          cache: true
+          cache: ${{ matrix.cache }}
           run_install: |
             - args: [--no-frozen-lockfile]