fix(ci): skip pnpm install for gitleaks job

gitleaks job only needs gitleaks binary, not node dependencies

Author: ryoppippi

.github/actions/setup-nix/action.yaml

@@ -5,6 +5,10 @@ inputs:
     description: 'Space-separated list of nixpkgs packages to install (e.g., "nodejs_24 pnpm_10 oxlint")'
     required: false
     default: 'nodejs_24 pnpm_10'
+  skip-pnpm-install:
+    description: 'Skip pnpm install step (useful for jobs that do not need node dependencies)'
+    required: false
+    default: 'false'
 runs:
   using: 'composite'
   steps:
@@ -24,5 +28,6 @@ runs:
         nix profile install $packages
 
     - name: Install pnpm dependencies
+      if: inputs.skip-pnpm-install != 'true'
       shell: bash
       run: pnpm install --frozen-lockfile

.github/workflows/ci.yaml

@@ -28,6 +28,7 @@ jobs:
         uses: ./.github/actions/setup-nix
         with:
           tools: gitleaks
+          skip-pnpm-install: 'true'
 
       - name: Run Gitleaks
         run: gitleaks detect --source . --config .gitleaks.toml