ci(actions): bump pnpm/action-setup from 5 to 6

Bumps [pnpm/action-setup](https://github.com/pnpm/action-setup) from 5 to 6.
- [Release notes](https://github.com/pnpm/action-setup/releases)
- [Commits](pnpm/action-setup@v5...v6)

---
updated-dependencies:
- dependency-name: pnpm/action-setup
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -22,7 +22,7 @@ jobs:
       - uses: actions/setup-node@v6
         with:
           node-version: "24"
-      - uses: pnpm/action-setup@v5
+      - uses: pnpm/action-setup@v6
       - run: pnpm install --frozen-lockfile
       - uses: actions/cache@v5
         with:
@@ -42,7 +42,7 @@ jobs:
       - uses: actions/setup-node@v6
         with:
           node-version: "24"
-      - uses: pnpm/action-setup@v5
+      - uses: pnpm/action-setup@v6
       - run: pnpm install --frozen-lockfile
       - uses: actions/cache@v5
         with:
@@ -85,7 +85,7 @@ jobs:
         with:
           node-version: "24"
           # Do NOT set registry-url — it creates an .npmrc that overrides OIDC
-      - uses: pnpm/action-setup@v5
+      - uses: pnpm/action-setup@v6
       - run: pnpm install --frozen-lockfile
       - uses: actions/cache@v5
         with: